Higher bone mineral density in Caucasian, hirsute patients of reproductive age. Positive correlation of testosterone levels with bone mineral density in hirsutism

Abstract

Objective The mechanisms leading to higher bone mineral density (BMD) in hirsute patients than in healthy controls have seldom been examined. We compared the metabolic, hormonal and bone metabolic parameters in hirsute patients and female controls and correlated BMD and bone metabolic parameters with testosterone, oestradiol and metabolic parameters. Patients Fifty‐one Caucasian, reproductive‐aged, hirsute patients referred to the outpatient clinic of an academic tertiary‐care medical centre and 63 healthy, female Caucasian controls matched for season, weight and age. Measurements BMD (hip, neck, lumbar and total BMD), bone metabolic parameters (osteocalcin, alkaline phosphatase, PTH, ionized calcium, phosphate and 25‐hydroxyvitamin D (25OHD)) and endocrine profiles (androgen status, oestradiol and insulin) were evaluated during follicular phase. Oestradiol measurement was repeated during cycle days 8–12. Results Lumbar and neck BMD levels were significantly higher in hirsute patients than in controls: (mean ± SD): lumbar BMD 1·10 ± 0·12 vs. 1·06 ± 0·10 g/cm² and neck BMD 0·91 ± 0·11 vs. 0·87 ± 0·12 g/cm², P < 0·05. Fasting insulin and free testosterone levels were significantly higher in hirsute patients than in controls. Free testosterone correlated positively with neck and hip BMD levels in hirsute patients. During multiple regression analysis, testosterone, oestradiol and waist/hip ratio (WHR) were found to have positive effects on BMD levels independent of body mass index (BMI). 25OHD levels were significantly lower in hirsute patients [42 (13–131)] than in controls [72 (27–196)] nmol/l (geometric mean ± 2SD), P < 0·001]. Conclusion Hirsute patients demonstrated significantly higher bone mineral density levels than controls, which could be explained by hyperinsulinaemia and higher testosterone levels in hirsute patients compared with controls. The pathogenesis for significantly lower 25‐hydroxyvitamin D levels in hirsute patients compared with controls needs to be evaluated in future studies.