Sex Differences and Exogenous Estrogen Influence Learning and Brain Responses to Prediction Errors

The effect of short-term increase of estradiol levels on sexual desire and orgasm frequency in women and men: A double-blind, randomized, placebo-controlled trial

Estradiol (E2) has been implicated in sexual functioning in both sexes. E2 levels change distinctively over the menstrual cycle, peaking around ovulation. Data on short-term effects of fluctuating E2 levels on sexual desire are however sparse and mostly based on observational studies. To fill this gap, we ran a double-blind, randomized, placebo-controlled study (N = 126) to investigate the effects of a short-term increase in E2 on sexual desire and orgasm frequency in healthy, young men and women. Circulating E2 levels were elevated through estradiol valerate (E2V) administered over two consecutive days to simulate the rise in E2 levels around ovulation. E2V had no effect on orgasm frequency and only minor effects on sexual desire. On average, the administered E2V dampened change in sexual desire compared to untreated participants with comparable baseline sexual desire in such a way that sexual desire was slightly reduced even in those with higher baseline sexual desire. These findings suggest that short-term increases in E2 have little effect on sexual function and are unlikely to explain the increase in sexual desire around ovulation.

Effects of 24-hour oral estradiol-valerate administration on hormone levels in men and pre-menopausal women

In order to translate the findings from the vast animal literature on the effect of 17β-estradiol (E2) on brain and behavior to humans, a placebo-controlled pharmacological enhancement of E2 levels for at least 24 h is necessary. However, an exogenous increase in E2 for such a prolonged period might affect the endogenous secretion of other (neuroactive) hormones. Such effects would be of relevance for the interpretation of the effects of this pharmacological regimen on cognition and its neural correlates as well as be of basic scientific interest. We therefore administered a double dose of 12 mg of estradiol-valerate (E2V) to men and of 8 mg to naturally cycling women in their low-hormone phase, and assessed the concentration of two steroids critical to hormone regulation: follicle stimulating hormone (FSH) and luteinizing hormone (LH). We also assessed any changes in concentration of the neuroactive hormones progesterone (P4), testosterone (TST), dihydrotestosterone (DHT) and immune-like growth factor 1 (IGF-1). This regimen resulted in similar E2 levels in both sexes (saliva and serum). FSH and LH levels in both sexes were down-regulated to the same degree. P4 concentration decreased in both sexes only in serum but not saliva. TST and DHT levels dropped only in men whereas sex-hormone binding globulin was not affected. Finally, the concentration of IGF-1 decreased in both sexes. Based on previous studies on the effects of these neuroactive hormones, only the degree of downregulation of TST and DHT levels in men might have an impact on brain and behavior, which should be considered when interpreting the effects of the presented E2V regimes.