Pituitary Disease

Pituitary Adenoma

Can either be:

• Functional - Produces hormones, so tends to be small at presentation

• Non-functional - Doesn’t produce hormones, so tends to be large at presentation

Typically presents with symptoms and signs of a SOL:

• Headache

• Bi-temporal hemianopia - compression of optic chiasm

• Diplopia - compression of CN 3/4/6

Management - Trans-sphenoidal surgery

Prolactinoma

This is the most common type of pituitary adenoma. Clinical features of it includes:

• Women - Oligomenorrhoea/amenorrhoea, Galactorrhoea, Infertility, Vaginal dryness

• Men - Erectile dysfunction, Reduced facial hair

• SOL - Headache, Bi-temporal hemianopia, Diplopia

Investigations:

• MRI brain

  • Microadenoma - lesion in the pituitary

  • Macroadenoma - SOL

• Serum prolactin

Management:

• Cabergoline - dopamine agonist, which leads to a decrease in prolactin

• Trans-sphenoidal surgery

Acromegaly

This is due to a GH-secreting pituitary adenoma. Clinical features of it includes:

• Large hands and feet

• Joint pains

• Facial changes - Frontal bossing, Large protruding jaw, Macroglossia

• Obstructive sleep apnoea

• SOL - Headache, Bi-temporal hemianopia

• Organ dysfunction - LV Hypertrophy, HTN, Diabetes

Investigations:

• IGF-1 as the initial screening tool

• OGTT as confirmation of the diagnosis - Glucose load will fail to suppress GH

• MRI brain

• Old photos for comparison

N.B. GH level isn’t a good diagnostic tool as it has a pulsatile release and fluctuates throughout the day.

Management:

• Trans-sphenoidal surgery - 1st line

• Somatostatin analogues (e.g. Ocreotide, Lanreotide) - blocks GH release

Cushing’s Syndrome

This is where there's excess cortisol secretion from adrenal gland. The most common cause of this is Cushing’s disease, which is an ACTH-secreting pituitary adenoma. Other causes include:

• Ectopic ACTH secretion e.g. small-cell lung cancer

• Adrenal adenoma

• Exogenous steroids

Clinical features:

• Face - Round “moon-face”, plethoric, acne

• Thinning of hair and skin

• Abdominal striae

• Central obesity

• Fat pad on upper back (buffalo hump)

• Easy bruising, poor skin healing

• Proximal myopathy

• Systemic - HTN, LVH, Diabetes, Osteoporosis

Investigations:

• Overnight DEXA suppression test - Failure to suppress cortisol in the morning suggests Cushing’s

• 24 hr urinary cortisol

• Plasma ACTH

• MRI brain

Management:

• Trans-sphenoidal surgery

• Metyrapone as steroid-blocking therapy before surgey

N.B. Most pts require steroid replacement therapy following surgery.

SIADH (Syndrome of Inappropriate ADH)

This is where there's excessive ADH production, which leads to lots of water reabsorption. This results in a high urine osmolality (concentrated) and euvolemic hyponatraemia (diluted blood). Causes of it includes:

• Pituitary tumour

• Malignancy, esp small-cell lung cancer

• Medications e.g. thiazide diuretics, carbamazepine, vincristine, NSAIDs

• Infection e.g. pneumonia

• Meningitis

• Idiopathic

Clinical features - Muscle aches and cramps, N+V, fatigue, confusion, coma, seizures

Investigations:

• U&Es

• Plasma osmolality - will be low

• Urine osmolality - will be high

• Urine sodium - will be high

• MRI brain

Management:

• Fluid restriction

  • Complication here is Central Pontine Myelinolysis - Avoid by correcting sodium slowly i.e. < 10 mmol/L/day

• Treat underlying cause

• Tolvaptan (2nd line) - ADH receptor blocker

Diabetes Insipidus

There are 2 types of this:

• Cranial - Lack of ADH

  • Causes - Idiopathic, tumour, trauma, brain infection

• Nephrogenic - Kidneys fail to respond to ADH

  • Causes are Iatrogenic e.g. lithium, genetics, electrolyte imbalance

Clinical features:

• Polyuria

• Polydipsia

• Hypernatraemia - lethargy, thirst, weakness, confusion

Investigations:

• U&Es

• Plasma osmolality - will be high

• Urine osmolality - will be low

• Urine sodium - will be low

• Fluid deprivation test - for diagnosis

  • Cranial DI - urine osmolality increases after desmopressin is given

  • Nephrogenic DI - urine osmolality stays low after desmopressin is given

• MRI brain

Management:

• Desmopressin if central

• Fluid maintenance if nephrogenic