Hormones and hair patterning in men: a role for insulin-like growth factor 1?
BACKGROUND: Androgens are important in hair growth and patterning, whereas growth hormone substitution enhances their effect in growth hormone-deficient men. No previous study has jointly evaluated the function of sex steroids, sex hormone-binding globulin (SHBG), and insulin-like growth factor (IGF-1) in determining hair patterning in men. OBJECTIVE: We assessed the relationship between circulating hormone measurements and both head and chest hair patterning in a sample of elderly men. METHODS: Fifty-one apparently healthy men older than 65 years of age were studied cross-sectionally. Head and chest hair patterning was assessed by a trained interviewer. Morning blood samples from all subjects were used for measurements of testosterone, estradiol, dehydroepiandrosterone sulfate, SHBG, and IGF-1. RESULTS: Results were obtained from logistic regression models, adjusting simultaneously for all the measured hormones and age. Men with higher levels of testosterone were more likely to have vertex baldness (odds ratio [OR] = 2.5, 95% confidence interval [CI: 0.9 to 7.8] per 194 ng/dL increment of testosterone). In addition, for each 59 ng/mL increase in IGF-1, the odds of having vertex baldness doubled (95% CI [1.0 to 4.6]). Those who were found to have higher circulating levels of SHBG were less likely to have dense hair on their chest (OR = 0.4, 95% CI [0.1 to 0.9] per 24 nmol/L increment in SHBG]). CONCLUSION: Testosterone, SHBG, and IGF-1 may be important in determining hair patterning in men.