Endocrine Abstracts

A 50-year-old half Jamaican gentleman was referred urgently to the endocrinology clinic with thyrotoxicosis. He had lost 2 stone in weight over a 2 month period and was complaining of lethargy, low libido and loose stools. His bloods showed a fT4>100 pmol/l, fT3 32.7 pmol/l, and TSH <0.02mU/l. Subsequently his TSH-R Ab returned elevated at 5.5IU/l (<2.9IU/l), confirming a diagnosis of Graves’ disease. His GP also checked his testosterone level on the initial bloods due to low libido. He was found to have an elevated total testosterone level of >50nmol/l (NR 8.6-29nmol/l) and an SHBG of >200nmol/l (NR 20-75nmol/l). He responded rapidly to carbimazole treatment and was treated using a dose-titration regime. Repeat testing of his testosterone level, once he was euthyroid, showed complete normalisation of his SHBG (58nmol/l) and consequently his total testosterone level (9.7nmol/l). This case highlights the link between hyperthyroidism and testosterone levels. Hyperthyroidism is thought to lead to an elevation in total testosterone in males due to an increase in hepatic synthesis of SHBG. SHBG also decreases the metabolic clearance rate of testosterone which contributes to the increase in serum total testosterone levels observed in hyperthyroid men. In most cases, normalisation of the sex hormones occurs once euthyroidism is achieved. This case serves as a reminder to always check thyroid function if faced with unusual sex hormone results in men.