Pseudohypoparathyroidism - Disorders of the parathyroids

Pseudohypoparathyroidism

Definition

This is a rare condition in which there is impaired response to circulating parathyroid hormone, and hence hypocalcaemia and hyperphosphataemia.

Aetiology

Failure of the target cell response to parathyroid hormone, thought to be due to a PTH receptor defect or its coupling to the second messenger system, adenylate cyclase.

Clinical features

Round face, short stature with short fourth and fifth metacarpals and metatarsals. Other features are the same as those of hypoparathyroidism. Some patients have the somatic manifestations, but without the biochemical abnormalities and clinical signs of hypocalcaemia and hyperphosphataemia. This is called ‘pseudopseu-doparathyroidism’.

Investigations

Low calcium with normal or high phosphate, unlike primary hypoparathyroidism normal or high PTH and alkaline phosphatase.

Management

Lifelong replacement therapy with 1,25(OH)2D3 or 1(OH)D3.