Changes in serum free testosterone, sleep patterns, and 5‐alpha‐reductase type I activity influence changes in sebum excretion in female subjects

Background/Purpose Sebum is thought to play an important role in acne vulgaris and sebum excretion rate ( SER ) is often used as a marker of efficacy in acne studies. This study explored factors that could induce intra‐subject variability in SER . Methods SER was measured twice, 7 days apart, on the forehead of 40 healthy subjects. At each visit, the following parameters were also evaluated: serum androgen levels, 5‐alpha‐reductase type I gene expression, forehead temperature, sleep habits, diet, facial washing routine, and UV exposure. Results There was a positive correlation between the time subjects fell asleep on Day 0 and the change in SER for the left ( P = 0.010; R = 0.402) and right sides ( P = 0.002; R = 0.467) of the forehead. There was a significant inverse correlation between SER and 5‐alpha‐reductase type 1 expression and between free testosterone levels and 5‐alpha‐reductase type 1 expression. In sub‐analyses performed on men and women, these correlations were only significant for women. Conclusion Variations in sleep patterns, free testosterone, and 5‐alpha‐reductase type 1 activity are associated with changes in sebum excretion in women. This could explain some of the inter‐subject variability in SER measured between visits in clinical studies.