Oestrogen in the brain plays key role in male desire

• The process whereby testosterone converts into oestrogen is vital for stimulating desire in the male brain
• This was uncovered in a study with genetically-engineered mice where the process was eliminated
• This finding could help develop more targeted medication to lower or increase sexual desire

When men have sex on the brain, a certain key gene is responsible for switching the process on, a new study has uncovered.

Published in Endocrinology, scientists from Northwestern Medicine conducted a study on mice where they genetically knocked out aromatase in male mice's brains. 

READ | Gender differences in mast cells can explain why we are more susceptible to immunological diseases 

Reduced sexual activity

The enzyme aromatase forms part of the biosynthesis process where testosterone is converted into oestrogen, and by taking it out of the mice's brains it reduced their sexual activity by 50%, even though the scientists increased their blood testosterone levels.

Normally, they would chase after female mice, but without the aromatase they were far less interested. Oestrogen is as important for men as it is for women in the regulation of sexual reproduction and the development of a healthy brain.

READ MORE | Your sex affects your genes for body fat, cancer and birth weight 

The researchers also looked at castrated mice, where testosterone-only treatment only partially restored sexual activity. However, when both testosterone and estradiol – an oestrogen steroid hormone – were combined, they fully regained their libidos, highlighting the role of aromatase in testosterone-dependent male sexual activity. 

"Aromatase deficiency, while very rare, has been reported in humans," write the authors. "The few aromatase-deficient men studied were reported to be heterosexual, with chronically elevated luteinizing hormone, follicle-stimulating hormone, and testosterone.

"Studies evaluating the effects of oestrogen therapy on libido in aromatase-deficient men reported significant improvements in the frequency of sexual activity following treatment, suggesting that oestrogens act either alone or synergistically with androgens to regulate sexual behaviour."

Targeted medication

This is the first study to demonstrate how testosterone is linked to male desire. It could change how male impotence is treated by targeting these specific elements in the brain alongside testosterone treatment.

"These studies provide foundational evidence that sexual behaviour may be modified through inhibition or enhancement of brain aromatase enzyme activity and/or utilisation of selective oestrogen receptor modulators," write the authors.

This could be useful for hypoactive sexual desire disorder – where the libido is constrained – and compulsive sexual desire. By targeting the specific regions, scientists could create treatment for these disorders without the side-effects of current medications.

READ | What is 'sex brain'?

^{Image credit: Pixabay}