Endocrine Abstracts

Hypercalcaemia is a recognised feature of hyperthyroidism due to accelerated bone turnover caused by thyroid hormone. When present, it is generally mild, usually with levels < 3.00 mmol/l. We present a case of a 19 year old male with thyrotoxicosis, who had severe hypercalcaemia and was also found to have possible co-existent adrenal insufficiency at the same time.

He presented with a 4 month history of weight loss, anxiety, tremors and palpitations. Blood tests revealed fT4 > 95.0 pmol/l, fT3 > 30 pmol/l and TSH < 0.05 mIU/l. He also had a Calcium level of 3.21 mmol/l and was admitted to hospital for IV fluids, carbimazole and propranolol. After 24 hours, his calcium levels rose to 3.53 mmol/l, co-incidental with a PTH of < 0.7 indicating that the significant hypercalcaemia was likely due to severe thyrotoxicosis. He received IV pamidronate treatment.

Two days into his admission he developed pyrexia, tachycardia, hypertension and increased agitation. This was managed as a thyrotoxic crisis with Propylthiouracil, iodine solution and hydrocortisone resulting in significant clinical improvement within 48 hours.

A cortisol level had been checked prior to steroid treatment and was found to be 117 mmol/l. A short synacthen test demonstrated adrenal insufficiency, with 0 minute cortisol level of 195 mmol/l and 30 minute cortisol of 247 mmol/l. He also developed rebound hypocalcaemia, necessitating calcium supplementation.

Within one month, his clinical symptoms and thyroid function have improved significantly. He has stopped calcium supplementation and remains normocalcaemic. He continues on hydrocortisone treatment. Once he is euthyroid, a repeat short synacthen test will be performed to establish whether this was relative adrenal insufficiency caused by severe hyperthyroidism or whether he has co-existent primary adrenal insufficiency.

This case highlights the need to consider thyrotoxicosis with concomitant adrenal insufficiency as a cause for severe hypercalcaemia, along with the management of a thyrotoxic crisis.