Gynaecomastia

Conditions which cause raised oestrogen levels. Conditions which cause low testosterone levels. Conditions which affect levels of sex hormone-binding globulin (SHBG), as it affects the free testosterone:oestrogen balance. Conditions which cause androgen resistance. Conditions which cause an increased conversion of androgens to oestrogens. Aromatase is one of the cytochrome P450 enzymes and is involved in the aromatisation of androgens to oestrogens eg, changing androstenedione to estrone and testosterone to estradiol. This enzyme is found in many tissues eg, brain, adipose tissue, blood vessels and the gonads. Enhanced adipose tissue, as in obesity, provides increased levels of the enzyme and, hence, increased production of oestrogens leading to gynaecomastia.