Pituitary Pathology

Question 1

What are the embryological derivations of the anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis)?

Answer 1

Anterior pituitary = Rathke’s pouch
Posterior lobe = outpouching of third ventricle

Question 2

What hormones do the anterior and posterior pituitary secrete?

Answer 2

Anterior: ACTH, FSH, LH, GH, TSH, PRL

Posterior: Oxytocin, ADH

Question 3

What is the most common cause of hyperpituitarism?

What is a minor cause?

Answer 3

Pituitary adenoma = most common

Minor - secondary hyperplasia from secretion of hormones by tumours.

Question 4

Where are pituitary adenomas located, and what can they cause?

Answer 4

Pituitary adenomas are slow growing benign neoplasms of the anterior pituitary.

They can cause:

• Hyperpituitarism or hypopituitarism
• Mass effect (intracranial pressure, pressure on hypothalamus/cranial nerves)

Question 5

How are pituitary adenomas classified?

Answer 5

Based on the hormone markers the tumour cells carry:

• Lactotrop
• Somatotroph (Gigantism, acromegaly)
• Corticotroph (Cushing’s disease)
• Gonadotroph
• Thyrotroph
• Plurihormonal

Question 6

How can mass affect create a hormonal imbalance?

Answer 6

The pituitary adenoma can compress the adjacent pituitary and damage normal cells

• Hyperfunction of one hormone
• Hypofunction of all the rest

Question 7

What is the most common cause and type of hypopituitarism?

Answer 7

Most commly, hypopituitarism is due to inadequate functional pituitary dissue.

• Destruction of pituitary tissue → Injury, ischaemia, infection

LEads to pan-hypopituitarism

Question 8

What is Sheehan’s syndrome?

Answer 8

Post-partum hypopituitarism due to haemorrhage

Question 9

What is pituitary apoplexy?

Answer 9

Sudden haemorrhage into the pituitary, leading to hypopituitarism.

Question 10

What is diabetes insipidus?

What is its pathology and consequences? What are its two forms?

Answer 10

Diabetes insipidus is the passage of large volumes of dilute urine.

• Kidney unable to resorb water from urine
• Thirst and polydipsia
• Risk of dehydration

Two forms:

• Central - Decreased ADH secretion from posterior pituitary
• Nephrogenic - Decreased ability to concentrate urine due to ADH resistance in kidney.

Question 11

What is SIADH?

What can it cause?

Answer 11

Syndrome of inappropriate ADH secretion.

• Hyponatremia
• Blood volume normal
• Cerebral oedema