Effect of hyperandrogenism and menstrual cycle abnormalities on bone mass and bone turnover in young women

Prolonged period of amenorrhoea are regarded as a risk factor for the appearance of osteoporosis. Amenorrhoea is a feature of different pathological conditions with heterogeneous endocrine profiles. We evaluated bone mineral metabolism in patients with polycystic ovary syndrome (PCOS), hypothalamic amenorrhoea and idiopathic hirsutism in order to establish the relative importance for the maintenance of normal bone mass of ovulatory cycles and androgen and oestrogen production.

Bone mineral density (BMD), bone turnover markers and endocrine profile were evaluated in 51 patients with PCOS, 24 patients with idiopathic hirsutism, 26 patients with hypothalamic amenorrhoea and 35 healthy women. Body mass index (BMI) ranged between 20.1 and 31.0 kg/m2, and age from 17 to 33 years. Thirty-eight of the PCOS patients were amenorrhoeic (< 4 menstrual cycles/year).

Spine and femoral BMD were significantly decreased and bone markers (serum osteocalcin, and urinary excretion of free deoxypyridinoline, cross-linked N-telopeptide and hydroxyproline) significantly increased in the patients with hypothalamic amenorrhoea, when compared to control subjects and the other two patient groups. In the sub-group of PCOS patients with amenorrhoea, spine and femoral neck BMD was significantly lower than in patients with idiopathic hirsutism and the non-amenorrhoeic PCOS patients. In all PCOS patients, spine and neck BMD were positively correlated (P < 0.05) with serum androstenedione and free testosterone levels.

The results of this study suggest that in patients with polycystic ovary syndrome the deleterious effect on bone of amenorrhoea is balanced by androgen overproduction.