Hyper- / Hypo-pituitarism and Pituitary Function

Question 1

Which pituitary hormones under inhibitory control by hypothalamus?

Answer 1

• Prolactin: inhibited by dopamine

- GH and TSH: inhibited by somatostain

Question 2

What is the function of ACTH?

Answer 2

• Stimulate growth of adrenal cortex

- Stimulate secretion of adrenal cortex hormones

Question 3

Physiology of ACTH?

Answer 3

• Pulsatile, diurnal variation (highest in AM, lowest at midnight)
• Polypeptide

Question 4

Inhibition of ACTH?

Answer 4

• Dexamethasone

- Cortisol

Question 5

What stimulates ACTH secretion?

Answer 5

• CRH
• Metyrapone
• Insulin-induced hypoglycemia
• Vasopressin
• Fever, pain, stress

Question 6

How may pituitary mass lesions present?

Answer 6

• Mass effect (visual field defects, diplopia, ptosis, headaches, CSF leak)
• Hypofunction
• Hyperfunction

Question 7

Conditions associated with hyperpituitarism?

Answer 7

-PRL (galactorrhea)
-GH (acromegaly / gigantism)
-ACTH (Cushing’s syndrome)
LH / FSH / TSH = rare.

Question 8

Ix pituitary adenoma?

Answer 8

• MRI
• Visual field testing
• Hypothalamic-pituitary hormonal function

Question 9

Aetiology of hypopituitarism?

Answer 9

8 I’s:

• Invasive
• Infarction
• Infiltratitve / inflammatory
• Infectious
• Injury
• Iatrogenic
• Immunologic
• Idiopathic

Question 10

Invasive causes of hypopituitarism?

Answer 10

• pituitary tumours
• craniopharygioma
• cysts
• mestastases

Question 11

Infiltrative causes of hypopituitarism?

Answer 11

• Sarcoidosis
• Haemochromatosis
• Histiocytosis

Question 12

Infectious causes of hypopituitarism?

Answer 12

• Syphilis
• TB
• Fungal (histoplasmosis)
• Parasitic (toxoplasmosis)

Question 13

Ix of hypopituitarism?

Answer 13

Triple bolus test
-IV insulin, GnH, TRH
Stimulates secretion of all pituitary hormones in normal individuals.