Hypoparathyroidism Flashcards
What is Hypoparathyroidism?
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.
Give 5 causes of hypoparathyroidism:
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
What are the risk factors for severe hypocalcaemia after a subtotal parathyroidectomy?
Severe preoperative hypercalcemia
Removal of a large thyroid adenoma
Elevated alkaline phosphatase
Chronic kidney disease
What is Type 1a pseudohypoparathyroidism?
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
What is Type Ib pseudohypoparathyroidism?
type Ib pseudohypoparathyroidism is less well known. Affected patients have hypocalcemia, hyperphosphatemia, and secondary hyperparathyroidism but do not have the other associated abnormalities.
What is type 2 pseudohypoparathyroidism?
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.
What is tetany?
stiffening and spasming of muscles
Give 5 psychological changes that may be seen in hypoparathyroidism
1) confusion
2) memory problems
3) irritability and restlessness
4) depression
5) hallucinations
How do we diagnose?
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.
What is the management for hypoparathyroidism?
supplemental calcium and vitamin D (calcitrol) which needs be monitored periodically for calcium, phosphate and renal function