Testosterone concentrations in hair of hypogonadal men with and without testosterone replacement therapy

Background: The measurement of testosterone (T) is essential for the diagnosis of male hypogonadism and for monitoring treatment. Samples need to be obtained at specific times in relation to the diurnal rhythm and therapeutic T injections. In this study, we explored the measurement of T in hair as an alternative method to assess gonadal status and long-term T exposure in men. SUBJECTS AND METHODS: Thirty-six male subjects comprising 17 healthy volunteers, 10 untreated hypogonadal men, and nine hypogonadal men receiving T injections were studied. T was measured in serum and in hair. T in hair was measured using a commercially available salivary T enzyme immunoassay kit adapted for this use. RESULTS: The T concentration in the hair of hypogonadal men receiving T injections was significantly higher than that in untreated hypogonadal volunteers, but not eugonadal men. Median T concentrations were 3.66 (range, 0.82-15.00), 0.94 (range, 0.33-3.68), and 1.85 (range, 0.58-3.06) pg/g hair, respectively. CONCLUSIONS: T in hair reflects gonadal status in men and may be useful for monitoring T therapy over several weeks to months in hypogonadal men.