Biological basis of child health 12: the endocrine system and common childhood endocrinopathies
Intended for healthcare professionals
CPD    

Biological basis of child health 12: the endocrine system and common childhood endocrinopathies

Kate Davies Associate professor of paediatric prescribing and endocrinology, London South Bank University and honorary research fellow in paediatric endocrinology, Queen Mary University of London, London, England
Sinead Bryan Independent endocrine nurse and quality assurance manager, Enviva Complex Care Limited, London, England

Why you should read this article:
  • To refresh your knowledge of the various hormones secreted by the endocrine system and their functions

  • To enhance your understanding of the presentation and management of common endocrinopathies seen in children

  • To count towards revalidation as part of your 35 hours of CPD, or you may wish to write a reflective account (UK readers)

  • To contribute towards your professional development and local registration renewal requirements (non-UK readers)

This article, the 12th in a series on the biological basis of child health, focuses on the endocrine system. This system works alongside the nervous system to regulate the functioning of the human body using chemical mediators called hormones. It is composed of several glands secreting a wide range of hormones that act on target cells in organs and tissues. Various functions of the human body are controlled by the endocrine system, including growth, puberty, metabolism and bone health. This article explores the anatomy and pathophysiology of the endocrine system, the effects of hormonal excesses or deficiencies on the body, and the presentation and management of endocrinopathies commonly seen in children.

Nursing Children and Young People. doi: 10.7748/ncyp.2021.e1342

Peer review

This article has been subject to open peer review and checked for plagiarism using automated software

@sausmash

Correspondence

kate.davies@lsbu.ac.uk

Conflict of interest

None declared

Davies K, Bryan S (2021) Biological basis of child health 12: the endocrine system and common childhood endocrinopathies. Nursing Children and Young People. doi: 10.7748/ncyp.2021.e1342

Published online: 05 July 2021

Aims and intended learning outcomes

The aim of this article is to enhance nurses’ knowledge of the endocrine system, including its functioning and the conditions that children and young people are likely to experience when this system is malfunctioning. After reading this article and completing the time out activities you should be able to:

  • Identify the glands of the endocrine system and the hormones they secrete.

  • Understand the effects of hormones on the normal functions of the human body.

  • Explain the effects of hormonal excesses or deficiencies on the body.

  • Identify the most common endocrinopathies in children and describe their presentation and management.

Key points

  • The endocrine system works alongside the nervous system to regulate the functioning of the human body using chemical mediators called hormones

  • The secretion of hormones by endocrine glands may occur in response to: internal chemical regulation and other internal factors; positive feedback mechanisms; and/or external factors

  • The secretion of hormones by endocrine glands, or the effects of hormones on their target cells, may cease in response to: the presence of inhibiting hormones; positive feedback mechanisms; and/or external factors

  • Examples of endocrinopathies that may be seen in children include isolated growth hormone deficiency, hypothyroidism, hyperthyroidism, hypoparathyroidism, diabetes mellitus, adrenal insufficiency and Cushing’s syndrome

Introduction

The endocrine system (Figure 1) works alongside the nervous system to regulate the functioning of the human body (Boore et al 2016) using chemical mediators called hormones. These are secreted by the endocrine glands and released into the blood to reach their target cells in organs and tissues.

Figure 1.

The endocrine system

ncyp.2021.e1342_0001.jpg

Hormone secretion is controlled by positive and negative feedback mechanisms, and the endocrine system is itself regulated by two of its glands – the hypothalamus and pituitary gland (Boore et al 2016). Clinical conditions seen in endocrinology clinics typically occur because of either insufficient or excessive hormone production, or sometimes due to an inability of the hormones to deliver their message because receptors on the targeted cells are not responding as they should.

The secretion of hormones by endocrine glands may occur in response to:

  • Internal chemical regulation and other internal factors such as calcium levels, blood glucose levels and electrolyte levels (Petty 2015).

  • Positive feedback mechanisms, whereby the output reinforces the original stimulus; for example, the release of oxytocin during childbirth (Waugh and Grant 2018).

  • External factors such as heat, cold, exercise and stress.

The secretion of hormones by endocrine glands, or the effects of hormones on their target cells, may cease in response to:

  • The presence of inhibiting hormones.

  • Negative feedback mechanisms, whereby elevated hormone levels prompt a slowing down of hormone secretion.

  • External or environmental factors, for example phytoestrogens or pesticides disrupting pubertal timing (Őzen and Darcan 2011).

Hormone secretion is sometimes regulated by rhythmic variations. For example, the activity of the adrenal cortex follows a circadian rhythm; the activity of the ovaries follows a monthly cycle; and growth hormone is secreted in a pulsatile manner, with an increase in secretory events (or pulses) at night (Moore et al 2019).

Hormones are classified into water-soluble hormones and lipid-soluble hormones (Petty 2015). Water-soluble hormones include insulin, adrenaline (epinephrine), growth hormone and oxytocin. They cannot cross cell membranes and instead bind to receptors on the outer surfaces of cell membranes. Therefore, if water-soluble hormones need to be replaced, they cannot be administered orally and need to be administered parenterally. Lipid-soluble hormones include steroid hormones (such as testosterone, oestrogens, glucocorticoids and mineralocorticoids) and thyroid hormones. They have the ability to cross cell membranes, which means they can be administered orally (Petty 2015).

Hypothalamus and pituitary gland

The hypothalamus and the pituitary gland secrete a range of hormones, many of which regulate the functioning of the endocrine system itself. The hypothalamic and pituitary hormones are detailed in Table 1.

Table 1.

Hypothalamic and pituitary hormones

Hormone secreted by the hypothalamusPituitary hormone it stimulates or inhibits the secretion ofTargetFunction
Growth hormone-releasing hormoneStimulates the secretion of growth hormone by the anterior pituitary glandBone and muscleGrowth hormone stimulates growth and reproduction of body cells
Thyrotropin-releasing hormoneStimulates the secretion of thyroid-stimulating hormone by the anterior pituitary glandThyroidThyroid-stimulating hormone stimulates the secretion of thyroxine and triiodothyronine by the thyroid
Gonadotrophin-releasing hormone (GnRH)Stimulates the secretion of luteinising hormone (LH) and follicle-stimulating hormone (FSH) by the anterior pituitary glandOvary, uterus, breasts, testesIn females: LH stimulates ovulation, prepares the uterus for implantation and stimulates the breasts to produce milk; FSH initiates the development of ova and oestrogen secretion. In males: LH stimulates testosterone production; FSH stimulates sperm production
Prolactin-releasing hormoneStimulates the secretion of prolactin by the anterior pituitary glandBreastsProlactin initiates and maintains milk production
Corticotrophin-releasing hormoneStimulates the secretion of adrenocorticotrophin hormone (ACTH) by the anterior pituitary glandAdrenal glandsACTH stimulates the secretion of glucocorticoids and androgens by the adrenal glands
Growth hormone-inhibiting hormone (somatostatin)Inhibits the secretion of growth hormone from the anterior pituitary glandPituitary glandGrowth hormone stimulates growth and reproduction of body cells and this function is disrupted by growth hormone-inhibiting hormone
Prolactin-inhibiting hormone (dopamine)Inhibits the secretion of prolactin from the anterior pituitary glandPituitary glandProlactin initiates and maintains milk production and this function is disrupted by prolactin-inhibiting hormone
Antidiuretic hormone (ADH)Does not stimulate or inhibit the secretion of another hormoneKidneysADH is stored in the posterior pituitary gland to be released when required. It increases the permeability of cell walls and tissue linings to water, which promotes water reabsorption and increases blood volume
OxytocinDoes not stimulate or inhibit the secretion of another hormoneUterus, breastsOxytocin is stored in the posterior pituitary gland to be released when required. It stimulates uterine contraction and the ‘let down’ reflex in milk production

(Adapted from Petty 2015)

Hypothalamus and related conditions

During gestation, the hypothalamus develops from forebrain tissue. The forebrain is one of the three vesicles that develop in the cranial end of the neural tube from week 3 of gestation – the other two being the midbrain and hindbrain. The hypothalamus is part of the midbrain and is located above the pituitary gland (Petty 2015). In addition to its role in regulating the endocrine system, the hypothalamus controls thermoregulation and fever, feeding and energy metabolism, and sleep and wakefulness.

Hypothalamic disease is rare, but it can result from malnutrition, head trauma, radiation therapy to the head, tumours or genetic disorders (Petty 2019). One example is hypothalamic obesity, which is a complex neuroendocrine disorder where energy regulation is affected (Haliloglu and Bereket 2015). Another example is Prader Willi syndrome, which is a genetic disorder caused by a dysfunction of chromosome 15q11-13. Its features include hyperphagia, food-seeking behaviours and excessive weight, and its incidence is approximately 1 in every 2,200 births (Prader Willi Syndrome Association UK 2021).

Antidiuretic hormone (ADH), which is secreted by the hypothalamus, controls urine output by acting on the distal convoluted tubules and collecting ducts in the kidneys, increasing their permeability to water (Waugh and Grant 2018). Decreased production of ADH results in central (or cranial) diabetes insipidus. Children with diabetes insipidus present with extreme polydipsia and polyuria. They will attempt to drink by any possible means, including from toilets and outdoor taps, and will get up throughout the night to pass urine.

The main causes of diabetes insipidus are pituitary tumours, head trauma and recent neurosurgery. If diabetes insipidus is permanent, it can be managed with ADH replacement (Di Iorgi et al 2012).

TIME OUT 1

Children with growth hormone deficiency will require treatment with daily growth hormone injections. However, the effects of this treatment are not instantaneous, so these children may become frustrated because they may not grow as quickly as they would like. How would you explain their condition and treatment to them? Visit the Child Growth Foundation website at www.childgrowthfoundation.org to read more about growth disorders

Pituitary gland and related conditions

The pituitary gland is a pea-sized gland located below the hypothalamus. Hypopituitarism is the inability of the pituitary gland to secrete hormones (Petty 2019). It may be congenital and associated with genetic disorders, or acquired, for example resulting from head trauma, infection or radiation (Urquhart and Collin 2016).

Isolated growth hormone deficiency is the most common pituitary endocrinopathy. It is also the most common reason why a child presents with short stature, which occurs in approximately 1 in every 4,000 children in the UK (Collin et al 2016). The diagnosis of growth hormone deficiency is often missed in early childhood because the child tends to be otherwise healthy; this diagnosis is often made once the child is at school, when the size difference with other children becomes increasingly obvious (Moore et al 2019).

Since growth hormone is secreted in a pulsatile manner, testing for growth hormone deficiency requires a stimulation test, which enables a sample to be obtained following a ‘stress response pulse’ of hormone release (Yedinak and Davies 2019). Growth hormone deficiency is treated with a daily subcutaneous injection of growth hormone at night until linear growth is complete.

Pituitary function can also be disrupted by tumours of the pituitary gland. These tumours are rare and usually benign, and they typically result in excessive hormone secretion. A prolactinoma is a type of pituitary gland tumour that secretes prolactin and usually presents at about puberty, with common symptoms including headaches, delayed puberty and galactorrhoea (spontaneous flow of milk from the breast not associated with childbirth or breastfeeding).

Treatment is with dopamine agonists (Hoffmann et al 2018). Cushing’s disease refers to an adrenocorticotrophin hormone (ACTH)-secreting pituitary adenoma, resulting in excessive glucocorticoid production (Storr and Savage 2015). Craniopharyngiomas are benign tumours that develop near the pituitary gland (Petty 2019) and account for 80% of tumours that disrupt the hypothalamic-pituitary pathway (Rosenfeld et al 2014).

Most children with pituitary gland tumours present initially with visual deficits and/or panhypopituitarism (inadequate or absent production of the anterior pituitary hormones), with or without diabetes insipidus (Steinbok 2015). The management of pituitary gland tumours depends on their site, but surgery will usually be the first-line treatment, followed by radiotherapy (Petty 2019).

Pineal gland and related conditions

The pineal gland is stimulated by light and produces the hormone melatonin (Petty 2015), which regulates the circadian rhythm. It is fully developed by the age of 7 years, when it is less than 1cm long, and tends to atrophy after puberty (Waugh and Grant 2018). Melatonin has a crucial role not only in sleep, but also in learning, short-term memory, pain perception and stress response.

It is likely that there is a link between abnormal melatonin secretion and disorders such as attention deficit hyperactivity disorder (ADHD) and autism (Bunn 2013). Melatonin replacement therapy can assist with sleep, and is well tolerated, in children with these disorders (Bunn 2013). It can also be prescribed to children and young people with no other underlying health conditions who experience sleep issues (Janjua and Goldman 2016).

Thymus and related conditions

The thymus is derived from the endoderm of the pharyngeal pouches. By week 10 of gestation, more than 95% of its cells are engaged in the production of T-lymphocytes (Palumbo 2008). At birth, the thymus weighs about 15g and it will grow until it reaches its maximum weight of about 40g during puberty, after which it decreases in size (Palumbo 2008).

The thymus is located in the anterior mediastinum (Boore et al 2016) and secretes thymosin, a hormone integral to T-cell development (Petty 2015), so the thymus has a role in the endocrine and immune systems.

Children with DiGeorge syndrome (22q11.2 deletion syndrome) are born with a hypoplastic thymus and associated hypoparathyroidism (Kreins et al 2020), resulting in a vulnerability to infection and hypocalcaemia (a low level of calcium in the blood) alongside cardiac anomalies and distinctive facial features.

TIME OUT 2

In the UK, screening for congenital hypothyroidism is not mandatory but it is strongly encouraged. How would you explain the benefits of screening to a parent who is reluctant to have their child screened? Visit tinyurl.com/NHS-blood-spot-test (NHS 2018) for further information about screening tests for newborns

Thyroid and parathyroid glands

Thyroid and related conditions

The thyroid is a butterfly-shaped gland situated at the front of the neck, wrapped around the trachea just below the larynx. It has two lobes connected by a stalk (isthmus) and is one of the largest glands in the human body. The thyroid starts to develop at about week 4 of gestation and, over the three following weeks, it descends to the hyoid bone to reach the lower part of the neck (Webster and De Wreede 2016).

The thyroid secretes thyroxine (T4), triiodothyronine (T3) and calcitonin as a direct response to thyroid-stimulating hormone (TSH). Iodine is essential for the formation of T3 and T4 (Waugh and Grant 2018), and is usually sourced from foods such as seafoods, salt and vegetables grown in iodine-rich soil. The secretion of T3 and T4 is controlled by the hypothalamic-pituitary-thyroid axis – since it is prompted by the secretion of TSH by the pituitary gland, itself prompted by the secretion of thyrotropin-releasing hormone by the hypothalamus (Table 1) – and moderated by a negative feedback loop (Bursell and Warner 2007).

Thyroid hormones are the major metabolic hormones and affect almost all body tissues. They have a role in the maturation of the brain during fetal development, they are involved in childhood growth and development, and they stimulate heat generation (Boore et al 2016). Calcitonin lowers calcium levels by accelerating calcium absorption by osteoblasts (cells that produce new bone tissue) (Petty 2015) and works with parathyroid hormone (PTH) in calcium metabolism (Boore et al 2016).

The most common conditions seen in children with a thyroid condition are hypothyroidism and hyperthyroidism. Congenital hypothyroidism affects 1 in every 3,000 newborns. Newborns and infants with congenital hypothyroidism may present with lethargy, sleepiness, suboptimal feeding, constipation and prolonged jaundice. Clinical signs of hypothyroidism in children include stunted growth of bones and teeth, hair loss, slow heart rate, excessive weight gain and short stature (Mondal et al 2017). Newborn screening for congenital hypothyroidism at day 5 of life has been practised in developed countries for the past 30 years (Ahmad et al 2017). If the screening results show raised TSH levels, imaging of the thyroid is required (Mondal et al 2017). Levothyroxine sodium is used to treat hypothyroidism.

Hyperthyroidism is rare in children (Uday et al 2019). Most cases are autoimmune and due to Graves’ disease, with about 100 new cases per year in the UK (Cheetham and Bliss 2016). Treatment is with antithyroid medicines (carbimazole or propylthiouracil), radioactive iodine or, in extreme cases, thyroidectomy.

Parathyroid glands and related conditions

The parathyroid glands are small masses of glandular tissue located at the back of the thyroid. Like the thymus, they are derived from the endoderm of the pharyngeal pouches. The parathyroid glands secrete PTH, one of the main regulators of calcium concentration in the blood.

The secretion of PTH is governed by low calcium levels (Markowitz et al 2016) and stimulates vitamin D production. PTH targets the skin, kidneys and bones, and it acts directly on osteoclasts (cells that break down bone tissue) to increase bone reabsorption. PTH and calcitonin work together to maintain adequate blood calcium levels, which are essential for enzyme action, blood clotting, muscle contraction and nerve impulse transmission (Waugh and Grant 2018).

Hypoparathyroidism occurs when the parathyroid glands do not secrete sufficient PTH or when PTH is not working as it should (Petty 2019), which results in hypocalcaemia and hyperphosphataemia (an elevated level of phosphate in the blood) (Snyder 2015). The most common cause of hypoparathyroidism is damage to or loss of the parathyroid glands, for example following thyroidectomy or radiation to the head or neck. Signs and symptoms are related to hypocalcaemia, and include tetany (involuntary contraction of muscles), convulsions, cardiomyopathy and respiratory arrest (Musson and Collin 2015), and their severity depends on the degree of hypocalcaemia. Treatment focuses on managing symptoms, as well as calcium salts and vitamin D supplementation (Snyder 2015).

Hyperparathyroidism occurs when there is too much PTH, which can cause calcium levels to increase, and phosphate levels to fall, outside the normal ranges (Petty 2019). It is usually due to a genetic and/or inherited defect in the parathyroid glands and is commonly seen in children with multiple endocrine neoplasia type 1 and 2 (Davies 2018a) or familial hyperparathyroidism.

Pancreas and related conditions

The pancreas is located below the stomach and above the duodenum. It has important roles in the endocrine and digestive systems, regulating blood glucose and releasing pancreatic polypeptides into the duodenum to assist digestion. The main pancreatic duct forms during week 7 of gestation. Endocrine cells comprise only 1% of the pancreas and are clustered in small groups called the islets of Langerhans, which form during month 3 of gestation and start secreting insulin during month 4 or 5 of gestation (Webster and de Wreede 2016).

The islets of Langerhans contain two main cell types (Petty 2015):

  • Alpha cells, which secrete glucagon. The role of glucagon is to increase blood glucose levels if they fall too low by prompting the liver to break down glycogen into glucose and by accelerating the conversion of lipids and proteins into glucose in the liver.

  • Beta cells, which secrete insulin. The role of insulin is to decrease blood glucose levels if they rise too high by prompting target cells to take up and use free glucose to convert it into glycogen, increasing lipid and protein synthesis from glucose, and slowing down the breakdown of glycogen into glucose, therefore decreasing blood glucose levels.

Glucagon and insulin work together to regulate blood glucose levels via a negative feedback loop, shown in Figure 2.

Figure 2.

Negative feedback loop regulating blood glucose levels

ncyp.2021.e1342_0002.jpg

TIME OUT 3

Children newly diagnosed with type 1 diabetes require education on how to recognise the signs and symptoms of hypoglycaemia and hyperglycaemia. How is this education provided in your clinical area? What could you do to improve how you and your colleagues educate children about hypoglycaemia and hyperglycaemia?

Diabetes mellitus

Type 1 diabetes

Type 1 diabetes is characterised by persistent hyperglycaemia that occurs because the pancreas is unable to secrete insulin due to the autoimmune destruction of beta cells (Couper et al 2018). An estimated 96,000 children under the age of 15 years are diagnosed with type 1 diabetes worldwide every year (Mayer-Davis et al 2018). Individuals with a first-degree relative who has type 1 diabetes have a 15-fold increased relative risk of developing the condition (Couper et al 2018).

At any age, the normal range for blood glucose levels is between 4mmol/L and 7mmol/L (Hanas 2015). In the presence of hyperglycaemia, random testing would show a blood glucose level >11.1mmol/L, or a fasting blood sample would show a blood glucose level >7.7mmol/L.

A child with type 1 diabetes typically presents with weight loss, increased thirst, polyuria and recurrent infections. If the condition is not diagnosed and not treated, the child will experience abdominal pain and potentially a coma (Petty 2019). The emergency presentation of type 1 diabetes also includes dehydration, vomiting, a smell of acetone on the breath, hyperventilation, shock and hypotension (Petty 2015), which are all indicators of diabetic ketoacidosis.

Diabetic ketoacidosis is a clinical emergency in which an absolute deficit of insulin leads to a lack of intracellular insulin in insulin-dependent tissues (muscle, fat and liver tissues), resulting in high levels of ketones causing acidosis. It is important that children’s nurses are aware of paediatric advanced life support guidelines (Wolfsdorf et al 2018) and their organisation’s policy for diabetic ketoacidosis management.

Children diagnosed with type 1 diabetes require insulin therapy. Insulin is a water-soluble hormone, so it needs to be administered subcutaneously or intravenously. Children will typically receive a basal bolus or multiple daily subcutaneous injections, as well as daily long-acting boluses and fast-acting insulins before meals (Eggleton 2012). An increasing number of children are being prescribed continuous subcutaneous insulin infusion via a pump (National Institute for Health and Care Excellence 2008, British Society for Paediatric Endocrinology and Diabetes 2020, Ziegler et al 2020).

Type 2 diabetes

Type 2 diabetes is characterised by hyperglycaemia that occurs because the insulin secreted by the pancreas cannot be used effectively. This results in features associated with insulin resistance syndrome such as hyperlipidaemia, hypertension, ovarian hyperandrogenism and non-alcoholic fatty liver disease. Risk factors for type 2 diabetes include having a family history of the condition, as well as being female and of non-white ethnic background. In the UK, the incidence of type 2 diabetes is nearly 1 in 100,000 children (Candler et al 2018).

Type 2 diabetes in children is becoming a public health concern worldwide, with obesity being a major contributing factor in the development of the condition (Mayer-Davis et al 2018). Type 2 diabetes can be treated through lifestyle management, although biguanides (such as metformin hydrochloride) or insulin may be required.

Adrenal glands and related conditions

The adrenal glands are a pair of triangular glands located above the kidneys and consisting of two layers: the adrenal cortex (outer layer) and adrenal medulla (inner layer). At week 9 of gestation, the adrenal cortex starts to develop into two distinct zones: the definitive zone and the fetal zone. The fetal cortex predominantly produces sex hormones (androgens) which, along with certain genes and the hormones secreted by the ovaries and testes, will contribute to the sex differentiation of the fetus at about week 6-7 of gestation (Davies 2019).

Adrenal cortex

The adrenal cortex is composed of three layers: the zona glomerulosa (outer layer), zona fasciculata (middle layer) and zona reticularis (inner layer).

The zona glomerulosa secretes mineralocorticoids, the main one being aldosterone – known as the ‘salt hormone’. Aldosterone focuses on maintaining water and electrolyte balance, stimulating the reabsorption of sodium and the excretion of potassium (Waugh and Grant 2018). Hyperaldosteronism (or primary aldosteronism) is the most common cause of secondary hypertension and it affects up to 13% of patients with hypertension (Dutta et al 2016). An excess of mineralocorticoids is extremely rare in children. It may be caused by an overdose of fludrocortisone acetate, by certain gene mutations or by aldosterone-secreting adrenal adenomas, which cause Conn’s syndrome. Mineralocorticoid deficiency is related to congenital adrenal hyperplasia, Addison’s disease, enzyme disorders and aldosterone resistance (or pseudohypoaldosteronism) (Donaldson et al 2019). Mineralocorticoid deficiency results in salt-wasting hyperkalaemia and metabolic acidosis. Children with mineralocorticoid deficiency usually present in the neonatal period with failure to thrive and dehydration.

The zona fasciculata secretes cortisol, which is the main glucocorticoid and is a steroid hormone. It has roles in metabolism, the inflammatory and immune responses, and the ‘fight-or-flight’ response (Waugh and Grant 2018). Cortisol secretion has a marked circadian rhythm, peaking between 4am and 9am and reaching its lowest level at around midnight.

The zona reticularis secretes androgens that are precursors to testosterone and oestrogen (Vasudevan and Brandt 2018). Adrenarche – the release of the androgens – is part of the pubertal process. It usually occurs before the development of secondary sexual characteristics, and involves pubic and axillary hair growth, acne and body odour (Novello and Speiser 2018).

Adrenal insufficiency

The most common cause of primary adrenal insufficiency in children is congenital adrenal hyperplasia, which accounts for 70% of all cases, while Addison’s disease accounts for about 15% of cases (Bowden and Henry 2018). Congenital adrenal hyperplasia affects about 1 in every 18,000 live births in the UK (Webb and Krone 2015). It results in reduced aldosterone and cortisol secretion and excessive androgen secretion. Girls with the condition present with genital virilisation (where female genitalia have the appearance of typical male genitalia) and are usually diagnosed shortly after birth (Davies 2019). Boys with the condition usually present in the emergency department at about two weeks after birth with failure to thrive, vomiting and suboptimal feeding, as well as hypoglycaemia and hyponatraemia (a low level of sodium in the blood) due to a salt-wasting crisis.

Lifelong glucocorticoid and mineralocorticoid replacement is essential, with oral hydrocortisone and fludrocortisone acetate replacing the missing cortisol and aldosterone, respectively (Moloney et al 2015). Infants will also require salt supplementation until they are fully weaned. Adherence to medicine regimens is essential to reduce side effects from insufficient dosing (for example lethargy and hypoglycaemia) or overdosing (for example weight gain and Cushing’s syndrome effects). Families should receive information about the disease and its management, notably the need to increase the dose of hydrocortisone if the child is unwell. Patients are advised to carry an emergency kit containing injectable intramuscular hydrocortisone in case of severe vomiting and diarrhoea (which would make them unable to absorb oral medicines), severe injury or collapse. They are also advised to wear a medical identity bracelet and carry a corticosteroid card (Moloney et al 2015).

Secondary adrenal insufficiency is caused by impaired ACTH secretion by the pituitary gland due to traumatic brain injury, radiation to the head, brain tumours or congenital conditions affecting the pituitary gland.

Cushing’s syndrome

Cushing’s syndrome occurs when there is hypercortisolaemia (an elevated level of cortisol in the blood), resulting in truncal obesity, impaired linear growth, a rounded ‘moon-shaped’ face, changes in the skin (for example acne, stretchmarks and/or bruising), hypertension and fatigue. The most common manifestation of Cushing’s syndrome in children is persistent weight gain alongside a lack of height growth. Cushing’s syndrome in children is usually caused by the exogenous administration of glucocorticoids (Keil 2013) and high-dose corticosteroids as part of their treatment for other conditions, for example cancer, respiratory disease, inflammatory bowel disease and cardiac disease. Other causes include ACTH-secreting tumours and adrenal tumours. Treatment usually requires a reduction of the exogenous medical treatment or surgery to remove the tumour (Keil and Stratakis 2008).

Adrenal medulla

When stimulated by the sympathetic nervous system, the adrenal medulla secretes adrenaline and noradrenaline (norepinephrine) (Waugh and Grant 2018). Along with cortisol, which is secreted by the adrenal cortex, adrenaline and noradrenaline are involved in the fight-or-flight response, mimicking the effects of the autonomous nervous system during times of stress (Petty 2015).

The absence of adrenal glands can occur because of congenital causes or surgery. It results in a reduced production of adrenaline and noradrenaline, but rarely causes a deficiency of these because they are also produced by the autonomic nervous system. Certain rare tumours, such as phaeochromocytomas (Davies 2018b), can cause an increase in adrenaline and noradrenaline secretion by the adrenal medulla, prompting episodic release and hypertension. These tumours need to be surgically removed.

Gonads and related conditions

The gonads are the ovaries in females and the testes in males. They are responsible for the onset and progression of puberty, the development of secondary sexual characteristics – breast development in girls, testicular and penile development in boys, and pubic and axillary hair growth in girls and boys (Pyra and Schwarz 2019) – and the development and maintenance of reproductive capability (Davies 2020). In both sexes, the hypothalamus produces gonadotrophin-releasing hormone (GnRH), which stimulates the pituitary gland to secrete luteinising hormone (LH) and follicle-stimulating hormone (FSH) (Table 1). The secretion of LH and FSH is pulsatile and in females it is also cyclical. Puberty begins when GnRH levels increase, although the exact mechanism triggering this is not yet understood (Zhu et al 2018).

Delayed and early puberty are commonly seen in paediatric endocrinology clinics. Delayed puberty is more common in boys than in girls, with constitutional delay being the most common cause (Wei and Crowne 2016). In both sexes, delayed puberty can also be caused by hypergonadotrophic hypogonadism or hypogonadotrophic hypogonadism.

Delayed puberty is treated with oestrogen and testosterone replacement, with the aim of developing secondary sexual characteristics and maturing gonadal function for future fertility. The transition of young people with delayed puberty into adult services needs to be managed sensitively, since it is important to consider the young person’s emotional needs alongside their physical needs.

Conclusion

The endocrine system has a crucial role in maintaining many of the fundamental functions of the human body. Therefore, children’s nurses need to be aware of how the endocrine system functions, its importance in enabling healthy growth and development, how hormonal excesses or deficiencies can affect the body and how common endocrinopathies in children are identified and managed.

Time out 4

Consider how your knowledge of the endocrine system and common endocrinopathies in children relates to The Code: Professional Standards of Practice and Behaviour for Nurses, Midwives and Nursing Associates (Nursing and Midwifery Council 2018) or for non-UK readers the requirements of your regulatory body

Time out 5

Now that you have completed the article you may want to complete the multiple-choice quiz and write a reflective account. To find out more go to rcni.com/reflective-account

Further resources

Child Growth Foundation

www.childgrowthfoundation.org

NHS (2021) Newborn Blood Spot Test

tinyurl.com/NHS-blood-spot-test

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