Establishing circadian rhythm profiles for salivary testosterone in women: evidence of decline during ageing

Androgens are increasingly known to play an important role in female health, development and well being. Alongside a controversial increase in androgen therapy there is a realisation that what actually constitutes androgen insufficiency is poorly understood. The aim of this study was to establish circadian profiles for salivary testosterone in healthy women from the age of 19 through 69 year old at 3 points during the menstrual cycle. Females were subdivided into these groups: 19-29, 30-39, 40-49 (peri- and post-menopausal), 50-59 and 60-69 years were investigated. The study was approved by the University College Ethical Committee and all subjects provided 8 saliva samples per day on the 4th, 14th and 21th day of their cycle. Post-menopausal women collected saliva samples on the 4th, 14th and 21th day of the calendar month. The women were not on any hormonal medication such as the contraceptive pill and HRT; nor did they suffer from any major illness. Testosterone levels were estimated using our in-house highly sensitive and specific ELISA method. The results indicated that female salivary testosterone concentration showed a circadian rhythm similar to that found in males, though at much lower levels. Perhaps more importantly, throughout the course of the day testosterone levels were highly variable with episodic fluctuations of individual data points exceeding the 09.00 hours levels by up to 90% on some occasions, indicating a role for the hormone in reproduction and sexual health. There was marked variation in testosterone concentration between day 4, 14 and 21 of the cycle, though not statistically significant except for the age group of 30-39 year (P<0.02, one-way repeated measure ANOVA). However, a significant decline in female salivary testosterone levels after the age of 39 years was evident. Day 4 of the cycle always exhibited near absence of salivary testosterone circadian rhythm. In contrast, day 21 testosterone values showed the best clear indication of the circadian rhythm profile compared to day 4 of the cycle. In conclusion, our study has established circadian profiles for female salivary testosterone and indicated that the testosterone levels were seriously low in some post-menopausal women and those above the age of 50 years that may justify some intervention to improve the health and well being of women.sch_diepub789pu