Obesity and Estrogen in Men

Excess fat tissue is not just an energy store but a hormonally active organ. In men with obesity it changes the balance of sex hormones: testosterone decreases, the proportion of estrogens increases. The editorial team breaks down how this mechanism works, why it is self-sustaining and which interventions really help.

Estrogen in the male body

Estradiol is often called the «female hormone», but for men it is just as necessary. It regulates bone mineralization and the closure of growth zones, participates in maintaining libido and erectile function, affects lipid metabolism, the work of the vessels and the brain. Men with rare genetic defects of aromatase or estrogen receptors have osteoporosis and metabolic disorders despite normal testosterone.

The greater part of estradiol in men is formed not in the testicles but in peripheral tissues — fat, muscle, bone, brain — from testosterone under the action of the enzyme aromatase (CYP19A1). That is, a man's estrogen level largely depends on how much substrate (testosterone) there is and how active the aromatase is.

Estradiol also participates in feedback: it signals to the hypothalamus and pituitary about a sufficient level of sex hormones and suppresses the secretion of gonadotropin-releasing hormone and luteinizing hormone (LH). It is precisely this property that becomes key in the mechanism of hormonal disorders in obesity.

So the problem is not estrogen as such, but the shift in balance: when, against a background of low testosterone, the relative proportion of estrogens rises, and the feedback signals «deceive» the pituitary.

Fat tissue as an endocrine organ

Adipocytes and stromal cells of fat tissue express aromatase. The greater the fat mass, the more testosterone is converted into estradiol, and androstenedione into estrone. Visceral fat, which accumulates around the internal organs, is considered especially metabolically active.

Fat tissue also secretes leptin, inflammatory cytokines (tumor necrosis factor-alpha, interleukin-6) and other signaling molecules. In people with obesity, resistance to leptin develops, and chronic low-grade inflammation, according to experimental data, suppresses the activity of the hypothalamic-pituitary-gonadal axis and the function of Leydig cells.

Another important factor is insulin resistance. Excess insulin suppresses the synthesis in the liver of sex hormone-binding globulin (SHBG). Because of this, total testosterone in men with obesity decreases partly «technically» — due to a smaller amount of carrier protein. But with significant obesity free testosterone falls as well.

This idea — the «hypogonadal-obesity cycle» — was formulated back in the late 1990s: excess fat lowers testosterone, and low testosterone promotes further accumulation of fat and loss of muscle. The cycle is self-sustaining until it is broken.

A vicious circle: obesity-associated hypogonadism

Modern endocrinologists distinguish functional hypogonadism associated with obesity. Its feature is a secondary nature: LH and FSH are low or unjustifiably «normal» with reduced testosterone. There are no structural lesions of the pituitary or testicles, and the disorder is at least partly reversible.

Large population studies, in particular the European Male Ageing Study (Wu et al., 2008), showed that obesity is one of the strongest independent predictors of low testosterone in middle-aged and older men — stronger than age itself. With weight gain the hormone level decreases, with weight loss it rises.

As for estradiol, the picture is not as simple as is sometimes presented in sports media. In many men with obesity the absolute level of estradiol is normal or moderately elevated, and what changes above all is the ratio of testosterone to estradiol. A significant rise in estradiol occurs more often with pronounced obesity.

Therefore «blocking estrogen» as a universal solution is the wrong path. Estradiol is needed for the bones and lipid metabolism, and a sharp reduction of it can worsen well-being, libido and bone density. Aromatase inhibitors have no official indication for the treatment of male hypogonadism associated with obesity and are used only in individual situations by decision of an endocrinologist.

Health consequences and how to detect them

Clinical manifestations of such a hormonal imbalance include decreased libido and erectile function, fatigue, reduced motivation, loss of strength. Also characteristic is gynecomastia — the proliferation of glandular breast tissue, which should be distinguished from lipomastia, that is, simple deposition of fat in the breast area.

Obesity also worsens fertility. Meta-analyses show an association of a high body mass index with decreased sperm quality and a higher frequency of oligozoospermia. To the hormonal mechanisms are added increased scrotal temperature, oxidative stress and concomitant metabolic diseases.

Low testosterone in men with obesity is associated with a higher risk of type 2 diabetes and cardiovascular diseases. It is hard to say what is cause and what is consequence here: most likely, both conditions mutually reinforce each other against a background of shared metabolic disorders.

For assessment the doctor determines morning total testosterone (repeatedly), SHBG with calculation of free testosterone, LH, FSH, prolactin, estradiol in the presence of gynecomastia, and also glycated hemoglobin, a lipid profile and liver function. It is important also to assess the presence of sleep apnea, which by itself lowers testosterone.

• waist circumference above the norm for men — a signal to assess metabolic and hormonal status;
• snoring and pauses in breathing during sleep — a reason to be examined for apnea;
• enlargement of the breast glands, especially painful or one-sided — a doctor's consultation is mandatory.

What helps: weight loss, training, medicine

The most substantiated intervention is a reduction of body weight. The meta-analysis by Corona and co-authors (2013) showed that both dietary weight loss and bariatric surgery raise testosterone levels, and the effect is proportional to the weight lost. After bariatric operations the increase is especially noticeable.

Physical training complements the diet: it reduces visceral fat, improves insulin sensitivity and helps preserve muscle mass during weight loss. A combination of strength and aerobic loads in most studies gives a better result for body composition than each type separately.

«Invisible» factors are also important: sufficient sleep, treatment of apnea (CPAP therapy), limiting alcohol, which enhances aromatization and disrupts liver function. Changing these habits often makes a noticeable difference in well-being even before significant weight loss.

Testosterone replacement therapy in hypogonadism associated with obesity is possible, but only with a confirmed diagnosis and symptoms and after discussion with an endocrinologist. The Endocrine Society guidelines emphasize that lifestyle change is the first step, and for men planning children exogenous testosterone is contraindicated because of the suppression of spermatogenesis.

Supplements advertised as «estrogen blockers» or «testosterone boosters» have no convincing evidence of effectiveness in this context. Money and effort are more rationally directed toward nutrition, training and medical examination.

Editorial conclusions

Obesity in men triggers a hormonal circle: more fat — more aromatization and insulin resistance — less SHBG and LH — lower testosterone — even more fat. This is a functional and largely reversible condition.

Estrogen is not an «enemy» that must be suppressed. The goal is to restore balance, and the main tool for this is a reduction of fat mass, physical activity and normal sleep.

Any hormonal interventions make sense only after a full examination and under a doctor's supervision.

We also recommend reading «Andrological Examination: What It Includes», «Stress and Libido» and «Is It True That Muscle Turns Into Fat».

References

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3. Corona G, Rastrelli G, Monami M, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol. 2013;168(6):829–843.
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