Pituitary Gland Conditions

Posterior pituitary gland

Diabetes insipidus (DI)

This is a condition characterised by the production of large volumes of dilute urine, which occurs due to poor water reabsorption by the kidney.

Central/Neurogenic DI

This refers to a failure of the pituitary gland to produce ADH.

It can occur idiopathically, due to a congenital defect in the ADH gene or secondary to central nervous system trauma (e.g., following neurosurgery) and tumours.

It is responsive to desmopressin treatment.

Nephrogenic DI

This is when the kidneys are unable to respond to ADH.

This can be due to genetic mutations in the ADH receptor, electrolyte abnormalities, but also secondary to drugs such as lithium and demeclocycline.

It is not responsive to desmopressin.

Dipsogenic DI/primary polydipsia

This is large amounts of urine production secondary to drinking too much water

Symptoms

Polydipsia (e.g., kids drinking bathwater) with life-threatening dehydration

Production of large volume (> 3 L/day) of dilute urine

Key tests

Blood tests – hypernatraemia and high plasma osmolality

Water deprivation test

Management

Aim to correct the underlying cause

For central DI, first line is desmopressin

For nephrogenic, bendroflumethiazide can be used as it has anti-diuretic actions

SIADH syndrome

This is a condition which leads to excessive ADH secretion. This leads to high amounts of water reabsorption from the kidney resulting in dilution of the blood.

Causes

Ectopic ADH production (e.g., small cell lung carcinoma)

CNS trauma/tumours

Drugs, e.g., SSRIs, tricyclic antidepressants, PPIs

Symptoms

Low volume, concentrated urine

Hyponatreamia which can lead to cerebral oedema giving headaches and seizures

Key tests

High urinary sodium concentration and osmolality

Blood tests show hyponatraemia (Na < 125 mM), low serum osmolality

Management

Water restriction

Demeclocycline, an antibiotic which reduces sensitivity of the collecting duct to ADH

ADH receptor antagonists e.g., vaptan drug family

Anterior pituitary gland

Hypopituitarism

This refers to decreased secretion of anterior pituitary hormones, which leads to symptoms according to the hormone(s) that are affected.

Causes

Hypothalamus – Kallman’s syndrome, tumour

Pituitary stalk – Trauma, Carotid artery aneurysm

Pituitary gland – Adenoma, apoplexy (bleeding of adenoma, haemorrhage of gland)

Symptoms

Hypopituitarism gives many symptoms due to the effect on the corresponding hormones.

Key tests

Hormonal profile to see which hormones are affected 

Management

Hormone replacement therapy

Sheehan syndrome

During pregnancy, the pituitary gland grows larger, but blood supply hardly increases.

High blood loss in childbirth (post-partum haemorrhage) can cause ischaemia and infarction of the pituitary gland, leading to the development of symptoms. 

Kallman Syndrome

This is a condition where there is a failure of the development of GnRH neurons derived from olfactory epithelium.

It causes low levels of LH and FSH, resulting in delayed puberty and hypogonadism.

It also causes anosmia (lack of smell), cleft lip and colour blindness. 

Pituitary adenoma

This is a benign tumour of the anterior pituitary cells.

It can be a microadenoma (<1cm) or macro (>1cm)

Can also be functional (hormone-producing) or non-functional (silent)

Most common tumour is prolactin secreting –> non-functional –> GH secreting –> ACTH secreting

Symptoms

Double vision, due to pressure on cavernous sinus pressing CN III, IV and VI

Bitemporal hemianopia, due to compression of the optic chiasm

Raised intracranial pressure if large, leading to nausea/vomiting, headaches

If hormone-producing, it presents with additional symptoms based on the type of hormone produced

Key tests

Pituitary blood profile (GH, prolactin, ACTH, FH, LH and TFTs)

MRI provides visualisation of the pituitary tumour

Management

Medical management of the hormones affected

Definitive treatment is removal of tumour. Options include surgery (e.g., transphenoidal hypophysectomy) and/or radiotherapy for residual/recurrent adenomas

Hyperprolactinemia

This refers to raised prolactin levels in the blood.

In addition to direct effects on lactation, raised prolactin inhibits GnRH which decreases testosterone and oestrogen giving secondary effects like osteoporosis.

Causes

Most often due to a pituitary adenoma increasing prolactin production

Reduced inhibition of pituitary gland, e.g., secondary to dopamine antagonists

Conditions which increase oestrogen e.g., pregnancy, polycystic ovary syndrome

Associated with acromegaly (1/3 of patients)

Primary hypothyroidism, as TRH stimulates prolactin release

Symptoms

As well as direct effects on lactation, raised prolactin inhibits GnRH which decreases testosterone and oestrogen giving secondary effects like osteoporosis.

Key tests

Blood tests show raised prolactin levels

Imaging, e.g., MRI is used if pituitary adenoma suspected of pituitary gland

Management

Dopamine agonists to reduce secretion, e.g., bromocriptine/cabergoline

If unresponsive to medical management, surgery can be offered

Acromegaly

This is a condition characterised by an increased secretion of growth hormone from the pituitary gland. It is most commonly due to a pituitary adenoma.

GH stimulates bone and soft tissue growth through IGF-1.

Symptoms

Can cause gigantism due to increased bone growth (if occurs in childhood)

Enlargement of the hands, tongue, jaw, and feet (increase in shoe size)

Acroparathesia (tingling in the hands and feet)

Pituitary tumour features, e.g., headache, visual disturbances, hyperprolactinaemia

Excessive sweating and oily skin, due to sweat gland hypertrophy

Complications

Growth of visceral organs can lead to cardiomyopathy

Hypertension

Secondary diabetes mellitus as growth hormone induces gluconeogenesis

Increased risk of colorectal cancer

Key tests

Blood tests – raised serum IGF-1 levels

Oral glucose tolerance test can be used:

Normally, GH levels are suppressed by the administration of glucose. In acromegaly there will be reduced suppression of growth hormone levels.

MRI pituitary fossa is used for imaging of the tumour

Management

Definitive management is surgery to remove the pituitary tumour

Octreotide is a somatostatin analogue, used as adjunct to surgery

Radiotherapy can be used in older patients or those not suitable for surgery

If above options are unsuccessful, pegvisomant (GH receptor antagonist) can be used