Hypoparathyroidism

Question 1

What is Hypoparathyroidism?

Answer 1

Hypoparathyroidism is a deficiency of parathyroid hormone often caused by an autoimmune disorder or by iatrogenic damage or removal of the glands during thyroidectomy or parathyroidectomy.

Question 2

Give 5 causes of hypoparathyroidism:

Answer 2

1) post-operative complications of thyroidectomy and other head and neck surgeries
2) DiGeorge syndrome
3) autoimmune destruction of parathyroid tissue
4) mutations of calcium sensing receptors (autosomal dominant hypocalcaemia)
5) hypomagnesia

Question 3

What are the risk factors for severe hypocalcaemia after a subtotal parathyroidectomy?

Answer 3

Severe preoperative hypercalcemia

Removal of a large thyroid adenoma

Elevated alkaline phosphatase

Chronic kidney disease

Question 4

What is Type 1a pseudohypoparathyroidism?

Answer 4

Type Ia pseudohypoparathyroidism (Albright hereditary osteodystrophy) is caused by a mutation in the stimulatory Gs-alpha1 protein of the adenylyl cyclase complex (GNAS1). The result is failure of normal renal phosphaturic response or increase in urinary cAMP (cyclic adenosine monophosphate) to PTH.
Patients usually are hypocalcemic and hyperphophatemic

Question 5

What is Type Ib pseudohypoparathyroidism?

Answer 5

type Ib pseudohypoparathyroidism is less well known. Affected patients have hypocalcemia, hyperphosphatemia, and secondary hyperparathyroidism but do not have the other associated abnormalities.

Question 6

What is type 2 pseudohypoparathyroidism?

Answer 6

In affected patients, exogenous PTH raises the urinary cAMP normally but does not raise serum calcium or urinary phosphate. An intracellular resistance to cAMP has been proposed.

Question 7

What is tetany?

Answer 7

stiffening and spasming of muscles

Question 8

Give 5 psychological changes that may be seen in hypoparathyroidism

Answer 8

1) confusion
2) memory problems
3) irritability and restlessness
4) depression
5) hallucinations

Question 9

How do we diagnose?

Answer 9

PTH and calcium measurement

PTH concentration should be measured as an assay of the intact molecule. Because hypocalcemia is the major stimulus for PTH secretion, PTH normally should be elevated in response to hypocalcemia. Thus,

Low or even low-normal PTH concentration in patients with hypocalcemia is inappropriate and suggests hypoparathyroidism.

An undetectable PTH concentration suggests idiopathic hypoparathyroidism.

A high PTH concentration suggests pseudohypoparathyroidism or an abnormality of vitamin D metabolism

Hypoparathyroidism is further characterized by high serum phosphate and normal alkaline phosphatase.

Question 10

What is the management for hypoparathyroidism?

Answer 10

supplemental calcium and vitamin D (calcitrol) which needs be monitored periodically for calcium, phosphate and renal function