Endocrine Abstracts

An 83-year-old gentleman was referred to the endocrine clinic with incidentally found abnormal thyroid function tests (TFT): TSH <0.02 (0.2–4.0 mU/l), free T₄ 20.4 (9–19 pmol/l), and free T₃ 7.6 (2.5–5.7 pmol/l). His TFT done 6 months previously were normal with TSH 1.21 mU/l and FT₄ 11.8 pmol/l. His past medical history included BPH, peripheral vascular disease and chronic kidney disease (CKD), and medications were tamsulosin, finasteride, aspirin, and lansoprazole. He denied having symptoms of hyperthyroidism, or family history of thyroid dysfunction. He was clinically euthyroid with no goitre or dysthyroid eye disease, but had bilateral gynaecomastia, normal body hair and testicular volumes. Direct enquiry revealed on-going breast enlargement for 2–3 months; there was no recent change in his drug history. Subsequent tests confirmed hyperthyroidism with TSH <0.02 mU/l, FT₄ 20.4 pmol/l and FT₃ 6.9 pmol/l. Other tests included negative thyroid-peroxidase antibodies, normal liver function tests, stable CKD stage 3, normal HCG, LH 13.4 (2–10 IU/l), FSH 12.6 (2–12 IU/l), testosterone 10.2 (8–30 nmol/l), ostradiol 98 (0–150 pmol/l) and SHBG 116 (14–71 nmol/l). A diagnosis of gynaecomastia due to hyperthyroidism was made and carbimazole-therapy initiated. He rapidly developed tiredness, albeit with normal FBC and unchanged TFT, and was changed to propylthiouracil 150 mg/day. After 10 weeks, his biochemical abnormalities and gynaecomastia improved. Thyroid ultrasound revealed an 8×6 mm nodule. Radioactive-iodine is planned as the definitive treatment for hyperthyroidism.

Gynaecomastia as the sole manifestation of hyperthyroidism is very rare, although is a well-documented clinical feature, reported in 2–44% of male patients with thyrotoxicosis. Altered oestrogen-to-androgen ratio, increased SHBG, enhanced peripheral aromatase activity, all contribute to hyperthyroidism-related- gynaecomastia, but exact mechanism is unknown. Gynaecomastia is common in men over 70 years (up to 55% at autopsy); could be due to aging-related endocrine/metabolic changes, drugs, medical conditions, etc. Aging, finasteride, lansoprazole, CKD, hyperthyroidism – multiple causes of gynaecomastia in our patient but improvement was noted on achieving euthyroidism. It is important to recognise hyperthyroidism as a reversible cause of gynaecomastia in the increasing elderly population.