Pituitary gland: Acromegaly and Giagantism, Diabetes Insipidus

Question 1

Define acromegaly?

Answer 1

refers to the pituitary tumour secreting excessive growth hormone AFTER closure of epiphyses.

Question 2

Define giagantism?

Answer 2

refers to the pituitary tumour secreting excessive growth hormone BEFORE the closure of epiphyses.

Question 3

Causes of acromegaly and giagantism?

Answer 3

pituitary adenoma -can be microscopic tumour or significant size tumour that compresses other structures.

Question 4

Presentation of acromegaly and giagantism?

Answer 4

• headaches
• hyperhydrosis = excessive sweating
• diabetes mellitus -insulin resistance
• reduced libido
• amenorrhoea
• excessive growth of soft tissue, internal organs (e.g. cardiomegaly)

Excess growth hormonecauses tissue growth:
- Prominent forehead and brow (frontal bossing)
- Coarse, sweaty skin
- Large nose
- Large tongue (macroglossia)
- Large hands and feet
- Large protruding jaw (prognathism)

Question 5

Diagnosis/IVx for acromegaly and giagantism?

Answer 5

• Serum IGF-1 levels are now the first-line test for acromegaly
• Oral glucose tolerance test (OGTT)
• Growth hormone measurements
• MRI/CT -pituitary adenoma

OGTT with GH levels at 0, 30, 60, 90, 120, 150 minutes
- Glucose normally suppresses growth hormone
- Acromegaly = growth hormone not suppressed or may rise

Question 6

Management of acromegaly and giagantism?

Answer 6

Surgery -removal of pituitary adenoma

Radiotherapy

Medical options to reduce the amount of growth hormone:
- Pegvisomantis agrowth hormone receptor antagonistgiven daily by asubcutaneous injection
- Somatostatin analogues(e.g.,octreotide, lanreotide) block growth hormone release
- Dopamine agonists(e.g.,bromocriptine) block growth hormone release

Question 7

Define Diabetes Insipidus?

Answer 7

refers to passing large volumes of dilute urine (>3L/day (or 24 hrs) due to REDUCED production or response to ADH (antidiuretic hormone).

Question 8

Causes of Diabetes Insipidus?

Answer 8

Can be divided into:
Causes of Cranial Diabetes Insipidus:
- brain trauma/surgery/infection
- genetic mutations in ADH gene
- Wolfram syndrome
- Vascular conditions (e.g. sickle cell disease)
- Inflammatory conditions (e.g. sarcoidosis)

Causes of Nephrogenic Diabetes Insipidus:
- meds (e.g. lithium)
- hypercalcaemia
- hypokalaemia
- kidney diseases

Question 9

What does ADH do? What happens in diabetes insipidus?

Answer 9

Also known as vasopressin

It stimulates water reabsorption from the collecting ducts in the kidneys.

In diabetes insipidus, the kidneys are unable to reabsorb water and concentrate the urine, which leads to polyuria and polydipsia.

Question 10

Presentation of diabetes insipidus?

Answer 10

• polyuria
• nocturia
• polydipsia (Excessive thirst)
• dehydration
• postural hypotension
• Enuresis (urinary incontinence)

Question 11

IVx for diabetes insipidus?

Answer 11

U&Es (hypernatremia, hyperuricemia)

Plasma and urine osmolality -high/normal serum osmolality (water loss may be balanced due to increased water intake)

Water deprivation test -urine abnormally dilute; low urine osmolality
- patient avoids water for 8 hours before the water deprivation test. After the test, urine osmolality is measured.
- If the urine osmolality islow,synthetic ADH(desmopressin) is given.Urine osmolality is measured over the 2-4 hours following desmopressin.

Question 12

Management of diabetes insipidus?

Answer 12

Treat underlying cause (e.g. pituitary tumour, metastases, head injury, meningitis, sarcoidosis, inherited).

Cranial DI:
- desmopressin (synthetic ADH; monitor SODIUM level)

Neurogenic DI:
- Ensuring access to plenty of water
- High-dose desmopressin
- Thiazide diuretics
- NSAIDs
- Bendroflumethiazide
- low protein
- low salt