Endocrine: Hypoparathyroidism

Question 1

Causes of hypoparathyroidism

Answer 1

Post-Surgical: most common cause. Removal of the parathyroid glands during neck surgery e.g. thyroidectomy

Autoimmune: Autoimmune destruction of the parathyroid gland

Congenital: Genetic disorders e.g. DiGeorge syndrome –> absent or malfunctioning parathyroid glands.

Idiopathic

Metabolic or Nutritional: Prolonged hypomagnesaemia can suppress parathyroid hormone (PTH) secretion. Similarly, excessive deposition of iron (haemochromatosis) or copper (Wilson’s disease) can damage the parathyroid glands.

Radiation: Radiation therapy to the neck, for conditions such as head and neck cancers, can damage the parathyroid glands leading to hypoparathyroidism.

Question 2

Clinical features of hypoparathyroidism

Answer 2

Hypocalcaemia symptoms:
- mild numbness or tingling of the extremities and around the mouth
- muscle cramps
- fatigue

Severe manifestations:
- tetany, carpopedal spasm, laryngospasm, and seizures

Question 3

What is Chvostek’s sign and Trousseau’s sign

Answer 3

Chvostek: twitching of the facial muscles in response to tapping over the facial nerve
Trousseaus: carpopedal spasm induced by occluding the brachial artery with a blood pressure cuff

Question 4

ECG changes in hypocalcaemia

Answer 4

Prolongued QT

Question 5

Management of hypoparathyroidism

Answer 5

Maintaining a slightly low to low-normal serum calcium level (reduce renal complications of hypercalcaemia)
- oral calcium supplements and active vitamin D analogues, such as calcitriol or alfacalcidol.

Diet: high calcium, low phosphate diet

Question 6

Affect of phosphate on calcium levels

Answer 6

PTH reduces renal phosphate reabsorption, leading to increased phosphate excretion

Reduced PTH action causes phosphate retention

Phosphate can combine with calcium in tissues and further reduce free calcium levels in the serum

Question 7

PTH affect on Vit D levels

Answer 7

PTH stimulates the conversion of 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D (calcitriol) in the kidneys

Calcitriol enhances intestinal calcium absorption

Reduced levels of PTH lead to diminished calcitriol production, decreasing calcium absorption from the intestines

Question 8

PTH affect on kidneys

Answer 8

PTH acts on the kidneys to promote calcium reabsorption

Without adequate PTH, more calcium is excreted in the urine

Question 9

PTH affect on bone

Answer 9

PTH stimulates osteoclast activity leading to bone resorption and the release of calcium into the bloodstream.

In the absence of sufficient PTH, this process is reduced, leading to decreased serum calcium levels.