Administration of testosterone undecanoate in postmenopausal women: effects on androgens, estradiol, and gonadotrophins.

Objective: To investigate serum androgens, estradiol, and gonadotrophins after treatment with testosterone undecanoate 40 mg daily in postmenopausal women.
Design: Ten postmenopausal women received 40 mg testosterone undecanoate orally every day for 4 days. Blood samples were drawn before and 2, 4, 6, and 8 hours after administration on the first day and then at 24, 48, 72, and 96 hours after administration of the first dose. Serum concentrations of testosterone, dihydrotestosterone, androstenedione, estradiol, sex hormone-binding globulin, follicle-stimulating hormone, and luteinizing hormone were analyzed.
Results: A rapid absorption of testosterone undecanoate was found with the highest concentrations of testosterone, dihydrotestosterone, and androstenedione 2-4 hours after administration. Significant increases from basal values were found for serum testosterone, dihydrotestosterone, androstenedione, and estradiol and a slight but significant decrease for sex hormone-binding globulin. Serum follicle-stimulating and luteinizing hormone levels were unchanged. Median levels of 3.2 nmol/L for testosterone and 3.6 nmol/L for dihydrotestosterone were recorded after the first day.
Conclusions: Testosterone undecanoate displayed a rapid absorption and turnover and may offer an alternative for androgen treatment in women. Expanded pharmacokinetic studies in larger and more homogeneous groups of postmenopausal women should be performed. The individual variations were considerable, and regular monitoring of testosterone serum levels to avoid overtreatment is recommended.