Endocrine Abstracts

Pseudohypoparathyroidism is a group of rare genetic disorders characterised by end organ PTH resistance in the body. It is a rare cause of hypocalcaemia. We present the case of a thirty-eight-year-old lady with no past medical history who presents for the first time to her general practitioner for a general check up and is incidentally found to have hypocalcaemia with a level 1.70 mmol/l. She was referred to hospital for the work up and treatment and was found to be hypocalcaemic on repeat testing. She was generally asymptomatic but complained of occasional spasms of the hand. On examination she had short stature and truncal obesity. As part of the initial management, calcium was replaced intravenously. Vitamin D deficiency was excluded (vitamin D level 80 nmol/l). Her magnesium was also normal. PTH was elevated at 171 ng/l and phosphate was elevated at 1.70 mmol/l. Her blood work was consistent with a diagnosis of pseudohypoparathyroidism. Based on these results, a genetic test was sent which confirmed a diagnosis of pseudohypoparathyroidism type 1 b. We commenced our patient alfacalcidol 0.5 mg twice daily and followed up in the endocrine clinic with improved calcium levels (2.02 mmol/l). Her first-degree relatives have been asked to attend for calcium measurements. The reported incidence of pseudohypoparathyroidism is 0.3 – 1 in 100,000 depending on the population however its exact incidence is unknown in Ireland. The clinical picture of pseudohypoparathyroidism includes hypocalcaemia, hyperphosphatemia, raised parathyroid hormone (PTH) levels and features of Albrights Hereditary Osteodystrophy (if type 1a or 1c) such as short stature, brachydactyly, obesity and intellectual impairment. Resistance to other hormones such as TSH, GHRH, FSH, LH can also occur depending on the subtype. This is usually a sporadic genetic disorder that occurs due to STX16 deletion leading to abnormal methylation of GNAS but can rarely be inherited.