Increased oestrogen may result from increased availability of androstenedione for extraglandular conversion, for example:
- liver disease especially cirrhosis - reduced hepatic extraction of androstenedione
- thyrotoxicosis - gynaecomastia occurs in about one third of men with thyrotoxicosis
- adrenal carcinoma - also, rarely, adrenal tumours may secrete oestrogen directly
- congenital adrenal hyperplasia
- starvation and refeeding - by a similar mechanism to that in liver disease
OR, may be due to increased testicular secretion, for example:
- testicular tumours: - stromal cell tumours ie. Leydig and Sertoli cell, may secrete testosterone and oestradiol autonomously - germinal cell tumours - embryonal carcinomas, choriocarcinomas, teratomas, and rarely, seminomas, produce hCG and hCG fragments which stimulate oestradiol and testosterone synthesis in unaffected areas of the testes - testicular choriocarcinomas with high aromatase concentration may convert circulating adrenal and testicular androgens to oestrogen
- bronchogenic carcinoma - cause increased plasma hCG levels which cause increased testicular oestradiol secretion. Other tumours may be associated with increased hCG secretion e.g. transitional cell tumours of the urinary tract
- true hermaphroditism - however, oestrogen probably comes from the ovarian elements
OR, from increased activity of aromatase enzymes in peripheral tissues which is seen both with age and with an increase in body fat (1).
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