Comparison of salivary versus serum testosterone levels in postmenopausal women receiving transdermal testosterone supplementation versus placebo

In Brief Objective: Clinical assessment of androgen action and its correlation to testosterone levels in women has been challenging. The current gold standard for measuring biologically active testosterone (T) is serum free T by equilibrium dialysis. Alternative methods are desirable due to the cost, complexity, and limited availability of the equilibrium dialysis method. Salivary testing has been proposed as a possible substitute for serum testing. This study compared salivary versus serum measurements of total T (TT), bioavailable T (BT; consisting of free T [FT] and albumin-bound T), and FT from samples collected simultaneously in women who were either receiving transdermal T patch supplementation (300 μg/d) or a placebo patch. Methods: Naturally and surgically postmenopausal women receiving concomitant hormone therapy were recruited to participate in a 24- to 52-week phase III trial of a 300 μg/day transdermal T patch for the treatment of hypoactive sexual desire disorder. Results: Initial analysis demonstrated high correlations between TT, BT, and FT levels (r = 0.776-0.855). However, there was no correlation with salivary T levels for any of the serum T subtypes (r = 0.170-0.261). After log transformation, salivary T correlated modestly with BT (r = 0.436, P < 0.001), FT (r = 0.452, P < 0.001), and TT (r = 0.438, P < 0.001). Conclusions: Although salivary testing of T concentrations is an appealing alternative because it is inexpensive and noninvasive, our results do not support the routine use of salivary T levels in postmenopausal women. In postmenopausal women, serum concentrations of free, total, and bioavailable testosterone did not demonstrate a strong correlation with salivary testosterone concentrations. These results do not support the routine use of measuring salivary testosterone in postmenopausal women receiving testosterone supplementation.