A 19-year-old man was admitted for further investigation for a six-month history of lethargy and depression. 11 months previously he had collapsed while on holiday in San Francisco when walking on a very hot day and was treated for dehydration. The patient had a history of epilepsy that was confined to the winter months! He was one of three siblings. His sisters, aged 17 and 20, were fit and well. On examination he was 1.52 m tall. He had a short neck and a left-sided divergent squint. There was no pallor. His heart rate was 68 beats/min and his blood pressure was 110/70 mmHg. There was a palpable thyroid goitre. Neurological examination was normal as was examination of all other systems. Blood tests performed by the GP are shown.
Hb 13 g/dl WCC 4.5 109/l Platelets 259 109/l Sodium 137 mmol/l Potassium 3.9 mmol/l Urea 4 mmol/l Creatinine 70 mol/l Calcium 1.8 mmol/l Phosphate 1.9 mmol/l Albumin 42 g/l Alkaline phosphatase 100 iu/l Bicarbonate 24 mmol/l TSH 18 iu/l Thyroxine 40 iu/l 24-h urinary calcium excretion Increased Chest X-ray Normal What is the most probable unifying diagnosis?
a. Hypoparathyroidism.
b. Hypothyroidism.
c. Pseudohypoparathyroidism.
d. Polyglandular endocrine deficiency type II.
e. Polyglandular endocrine deficiency type I
Answer:
The patient has low calcium and high phosphate levels in the absence of abnormal renal function. The differential diagnosis is between hypoparathyroidism and pseudohypoparathyroidism. Pseudohyoparathyroidism is due to the end-organ resistance to the effects of PTH,
which are mediated via adenylate cyclase. The morphological features in this patient (short stature, squint) are more common in pseudohyoparathyroidism. Furthermore, the patient has biochemical hypo thyroidism, which is a more common association with pseudohypoparathyroidism and is due to end-organ resistance to the actions of TSH, which also mediates its effects via adenylate cyclase.