Reversible male subfertility due to hyperthyroidism.

A 26-year-old man with a one-year history of attempted conception was referred to a male subfertility clinic. Two previous semen analyses had disclosed oligospermia with sperm counts of 11 x 109/1 on both occasions (figure). He had had classical symptoms of thyrotoxicosis for five years and 18 months earlier had been investigated for palpitations. Examination showed a diffuse goitre, tremor, and tachycardia; vitiligo was present on the arms, trunk, and penis. There was no gynaecomastia and the testes were normal. Hyperthyroidism was confirmed biochemically: serum thyroxine concentration was 267 mmol/l (20-7 4g/100 ml) (normal range 70-160 mmol/l; 5-4-12-4 ,ug/10O ml) and free thyroxine index >500 (normal range 70-180). Basal serum luteinising hormone, follicle-stimulating hormone, and prolactin concentrations were normal. Serum testosterone concentration was considerably raised at 68-9 nmol/l (1-9 ,tg/ml) (normal range 10-35 nmol/l; 0-2-10 ,ug/ml). Restoration of normal thyroid function with treatment with carbimazole therapy was associated with a fall in serum testosterone concentration to 20-5 mmol/l (591 mgf100 ml) and a progressive increase in sperm count. After 12 months of treatment his wife conceived and subsequently gave birth to a normal son.