Estrogen
- Has been considered incorrectly to be important only in women
- An imbalance of this important hormone in men will lead to a significantly increased risk for atherosclerosis and cardiovascular disease.
- It has been shown that men with only slightly elevated levels of estrogen actually doubled their risk of stroke68.
- Estrogen is thought to have an adverse effect on blood lipid composition increasing the risk of a cardiovascular event in men with elevated estrogen blood levels69.
Estrogen in men
- Estrogens in men are derived from circulating androgens through aromatization of testosterone and androstenedione by the aromatase enzyme to form estradiol and estrone, respectively.
- Most testosterone in a man's body comes from the testes and estrogen is then produced by aromatization of testosterone and androstenedione.
- If men have too much aromatase activity, then estrogen levels will be high
- Low aromatase activity in some men may also cause a man to have low estrogen levels and this can lead to an increase in mortality as well.
- However, it is more likely that diminishing testosterone production from the testes as men age leads to a lower level of conversion to estrogen and in this instance, testosterone and estrogen balance can be restored by providing a man with testosterone. It is well worth the trouble to check your blood testosterone and estrogen levels and to discuss testosterone replacement with your doctor if these levels have been found to be low. This link will provide you with valuable information: Testosterone in men.
Testosterone, aromatase and estrogen levels
Aromatase activity increases with age and body fat mass70.- Testosterone is converted to estrogen by aromatase enzyme activity and aromatase is a member of the cytochrome P450 superfamily of enzymes.
- Aromatase activity is 10 times higher in preadipocytes than mature adipocytes and aromatase activity is also site dependent with higher aromatase activity in preadipocytes in subcutaneous adipose tissue than omental (visceral or deep abdominal) fat74.
- Estrogen actually stimulates preadipocyte proliferation and growth of mature adipocytes (fat cells)74.
- Estrogen derived from adipose (fat) tissue drive fat to subcutaneous and breast depots76.
- High aromatase activity will diminish testosterone levels in men putting them at increased risk of prostate cancer and heart disease71.
- Low testosterone levels in turn can result in low estrogen levels and this puts a male individual at increased risk of osteoporosis, cardiovascular disease and stroke.
- Men with benign prostate enlargement often have higher levels of estrogen and it is thought that estrogen has a role to play in the causation of benign prostatic hyperplasia (BPH) in men72. Benign prostatic hyperplasia is predominantly a stromal cell overgrowth problem and estrogen has been shown to stimulate stromal cells in culture73.
Hypogonadotrophic hypogonadism - how estrogen drives down testosterone levels in males
- It is interesting that a negative feedback mechanism to decrease testosterone production occurs not only by testosterone acting on the hypothalamic-pituitary-gonadal (HPG) axis but also by estrogen in men.
- In the hypothalamus, gonadotropin-releasing hormone (GnRH) travels to the anterior pituitary gland and stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
- FSH stimulates spermatogenesis (sperm formation) in the sertoli cells of the testes and LH stimulates the leydig cells to produce testosterone.
- Estrogen can shut down this mechanism by decreasing GnRH produced by the hypothalamus thus decreasing FSH and LH and as a result this will decrease the action of LH on the leydig cells of the testes shutting down production of testosterone.
- So not only is testosterone being channelled into the production of estrogen through aromatase activity in obese men, it is also shutting down the production of testosterone through the central nervous system.
