By examining these relationships with and without suppression of estrogen synthesis, we found that lean mass, muscle size, and strength are regulated by androgens; fat accumulation is primarily a consequence of estrogen deficiency; and sexual function is regulated by both androgens and estrogens. In our study, we manipulated testosterone doses with or without an aromatase inhibitor. Changes in lean mass, thigh muscle area, and leg strength were attributable to changes in testosterone levels, whereas changes in fat measures were primarily related to changes in estradiol. Among men who were blocked from producing estrogen, the researchers saw increases in body fat at all levels of testosterone supplementation — but there was no effect on lean muscle mass, muscle size, or leg strength.

In conclusion, these data suggest that in the male 1) estrogens do not contribute significantly to the changes in body composition and protein synthesis observed with changing androgen levels; 2) estrogen is a main regulator of the gonadal-pituitary feedback for the gonadotropin axis; and 3) this level of aromatase inhibition does not negatively impact either kinetically measured rates of bone calcium turnover or indirect markers of bone calcium turnover, at least in the short term. These studies have shown that specific blockade of the aromatase enzyme for 10 weeks did not have catabolic effects on protein metabolism or intermediate metabolism of substrates, and it did not affect body composition, quantifiable measures of muscle strength, or bone calcium metabolism in healthy eugonadal young men. Body composition (weight, fat-free mass, percent fat mass) and skeletal muscle strength were not affected by the suppression of E2 concentrations.

First, our results indicate that increases in serum levels of total testosterone and estradiol were associated with significant increases in abdominal muscle mass in men. In this analysis, we demonstrate a positive association between total testosterone levels with abdominal muscle area and radiodensity, whereas estradiol showed a similar strong association with abdominal muscle area but not radiodensity. Additionally, SHBG was significantly and inversely associated with abdominal radiodensity although a negative trend was presented for abdominal muscle index.

No statistically significant differences were observed for testosterone, free testosterone, 3α-Diol-G, estradiol, or free estradiol in exercisers versus controls. In addition, there were positive correlations between BMI or body weight and estradiol or free estradiol (ranging from 0.20 to 0.37, all P < 0.05). We found no significant effects of this exercise intervention on testosterone, free testosterone, 3α-Diol-G, estradiol, or free estradiol.

Current evidence indicates that estrogens have a role in maintaining muscle mass. Collectively, evidence that estrogen deficiency causes dysregulation in muscle protein turnover with the balance tipping away from protein synthesis and toward protein degradation and thus contributing to the loss of muscle mass is weak. Thus, when estrogen is deficient it appears that apoptotic pathways contribute to the loss of muscle mass.

Because testosterone is the substrate of aromatase enzyme, testosterone deficiency is supposed to lead to relative estrogen deficiency. However, considering the inter-individual differences in the rate of conversion of testosterone to E2, men with low testosterone do not necessarily have insufficient estrogen levels. In hypogonadal men with obesity, we found that higher aromatase activity was associated with higher estradiol levels despite low testosterone, illustrating that estrogen levels depend on both testosterone availability and aromatase activity.

The results of these cross-sectional analyses suggest that **higher levels of E2 and the ratio of E2/T in men are associated with greater fat mass**, whereas higher levels of T and to some extent SHBG are associated with **lower fat mass**.[2] The positive association between E2 and fat mass may be explained in part by the fact that **men with higher BMI tend to have more E2 due to increased aromatase activity**.[2] Our longitudinal analyses of hormone levels and change in anthropometric measures, although limited in scope, indicate that **these associations are driven by the influence of adipose tissue on hormone levels**.[2]

This reproducible association between **serum estrogen levels and adiposity in men** has been ascribed to **increased adipose tissue aromatase activity in the setting of fat mass accumulation**.[1] Therefore, men with **relative estrogen deficiency due to lower ESR1 expression in adipose tissue or low circulating estradiol, or both, tend to have higher fat mass and insulin resistance**, thus pointing out a main role of estrogens on weight and body composition in men.[4] Thus, **estrogens, not only androgens, are responsible for crucial physiological functions in men like fertility, reproduction, and bone health**.[4]

In summary, falling testosterone levels with age are associated with the loss of lean muscle and bone mass. As expected, low testosterone was correlated with poor muscle strength. These findings support the concept that testosterone, rather than estrogen, is the primary sex steroid regulating skeletal muscle mass and strength in men, although estrogens have important roles in bone metabolism.

In a small study of men whose hormone levels were altered to mimic low testosterone — and in some cases, to completely inhibit estrogen production — it appeared that androgen deficiency accounted for decreases in lean mass, muscle size, and strength, while a lack of estrogen was responsible for increases in body fat. Overall, they found that changes in lean mass, thigh muscle, and leg strength were attributable to changes in testosterone levels, while changes in fat measures were primarily related to changes in estrogen. Among men who were blocked from producing estrogen, the researchers saw increases in body fat at all levels of testosterone supplementation — but there was no effect on lean muscle mass, muscle size, or leg strength.

Appendicular skeletal mass (ASM) was **positively associated with total testosterone (TT; P<0.001), free testosterone (FT; P<0.001), and total E2 (P<0.001) but not with free E2 (P=0.102)**.[13] Testosterone level was related to both **muscle mass, strength and physical performance**.[13] Total E2 level, though **related to muscle mass positively, affected muscle strength adversely in older men**.[13]

Peripheral androgen aromatization is enhanced in subjects with increased body mass index (BMI). Massively obese men show markedly increased plasma oestradiol concentrations and low testosterone concentrations. After weight reduction these alterations can be reversed, underlining the importance of adipose tissue for peripheral aromatization of androgens.

Intriguingly, this reduction in testosterone tracks with the gradual decline in muscle mass observed with age, i.e., ~1–3% decline in circulating testosterone and 1–2% loss of muscle mass in men, perhaps suggesting declines in endogenous testosterone may be linked to loss of muscle mass. This reduction can eventually lead to very low resting concentrations of circulating testosterone particularly in men, creating the so-called andropause. The article discusses how lower testosterone and growth hormone with aging are associated with reduced muscle mass and strength, whereas the role of estrogens in male skeletal muscle is less clearly defined.

Enhanced **skeletal muscle aromatase activity in male mice induces weight loss, improves metabolic and inflammatory outcomes and mitigates the negative effects of a high-fat diet (HFD)**.[10] Selective upregulation of muscle E2 using our SkM-Arom↑ model resulted in **increased levels of E2 which facilitated weight loss (−11%)**.[10] In summary, utilizing a novel mouse model, we show that **E2 originating from skeletal muscle mitigates the negative consequences of HFD-induced obesity in males**, indicating that **skeletal muscle can be a source of circulating estrogen**, rather than high muscle mass causing estrogen deficiency.[10]

The researchers reported that testosterone affected only lean body mass and muscle strength, while, as in women, estrogen played a major role in fat accumulation in men. They explained that in men, a decline in estrogen, not just testosterone, was associated with increased belly fat and metabolic changes. These findings indicate that estrogen has important physiological roles in middle‑aged men, and that low estrogen (deficiency) contributes to central obesity and related symptoms.

A certain amount of estrogen is essential for male reproductive capacity. If it is too low or too high, infertility can occur. Healthy libido, erection, and sperm production require an appropriate level of estrogen. Too little leads to infertility and too much also leads to infertility. Estrogen deficiency in men is also associated with continued bone growth and impaired bone maturation, whereas excess estrogen stops growth.

Chronic exercise decreased androgens and estradiol in females but increased androgens in males. Intramuscular androgens were positively associated with muscle mass and strength in males. Studies involving both animals and humans have shown that the levels of sex steroid hormones and the enzymes responsible for their production in skeletal muscle are increased through both acute and chronic exercise.

Studies involving both animals and humans have shown that the levels of sex steroid hormones and the enzymes responsible for their production in skeletal muscle are increased through both acute and chronic exercise. In human studies, exercise has been shown to restore muscle sex steroid hormones, with significant correlations observed between these hormones and muscle mass and strength. Acute exercise enhances the expression of muscle steroidogenic enzymes and sex steroid hormone levels, with notable sex differences in the response of muscle steroidogenesis to acute exercise.

Estradiol deficiency clearly predisposes males to increased adiposity and metabolic dysregulation. Several experimental and clinical findings in humans collectively indicate that estradiol has important effects on energy homeostasis and adiposity in men. However, testosterone appears to have a dominant role in the regulation of lean body mass and muscle strength, with estradiol playing a more modest, complementary role in skeletal muscle in males.

By comparison, the muscular estradiol concentrations were significantly higher in exercised relative to resting male rats but were unchanged in female rats. Basal muscular estrogen levels did not differ between sexes and were elevated by exercise only in males. Therefore, in exercising skeletal muscle, estrogen synthesis may increase in males while testosterone synthesis may increase in females.

Total E2 level, though related to muscle mass positively, affected muscle strength adversely in older men. Testosterone was related to both muscle quantity and quality. It was positively correlated with muscle mass and was associated with muscle strength and physical performance independent of muscle mass. Total E2 level, though related to muscle mass positively, was associated with weaker muscle strength in older men.

In unadjusted analyses, both **total estrone and estradiol were significantly associated with self-rated health** at Examination 8.[5] After adjusting for age, BMI, smoking, comorbidity index, and total testosterone, **estradiol level at Examination 7 was a significant predictor of fair or poor self-rated health** at Examination 8.[5] These data show that **circulating estrogen levels in community-dwelling men are related to health status and mobility**, with low or high levels having clinical implications, but they do not indicate that greater muscle mass per se causes estrogen deficiency.[5]

Low testosterone levels are known to cause decreased muscle mass, reduced libido, and depressed mood in men, a constellation often referred to as male menopause. On average, testosterone levels decline by about 1% per year after the age of 40. This decrease in testosterone is associated with loss of muscle mass rather than an increase in muscle mass, highlighting that hormone deficiency in men typically reduces muscle, not that excessive muscle mass intrinsically causes hormone deficiency.

Most experts agree that the **normal male range for the main form of estrogen, estradiol, is about 10 pg/mL to 50 pg/mL**.[6] Obesity can **raise estrogen levels**, but some research suggests that it does not raise them above the normal range.[6] This overview identifies **obesity, certain medications, and medical conditions as causes of high estrogen in men**, not high muscle mass.[6]

Testosterone is involved in maintaining and generating muscle; when levels fall, muscle mass decreases and muscle strength can weaken. This article explains that hormone deficiency leads to a loss of muscle mass and strength. It does not describe excessive muscle mass as a cause of estrogen deficiency, but rather shows that sex‑hormone deficiency tends to reduce muscle tissue in both sexes.

Muscle is sometimes called the "second testis" because when muscle grows, male hormone (testosterone) increases. Muscle contains an enzyme that converts the intermediate metabolite DHEA into male hormone. Therefore, an increase in muscle mass leads to an increase in blood male‑hormone levels and can improve sexual function. This explanation treats greater muscle mass as a factor that raises androgen levels, not as a cause of estrogen deficiency.

The results of these cross-sectional analyses suggest that higher levels of E2 and the ratio of E2/T in men are associated with greater fat mass, whereas higher levels of T and to some extent SHBG are associated with lower fat mass. These findings indicate that in men, estradiol is more strongly related to adiposity, whereas testosterone is more strongly related to lean mass and muscle-related parameters. Sex steroid hormone levels thus have distinct associations with different components of body composition in men.

Other possible symptoms of **high estrogen** that may happen along with other hormone imbalances include: reduced sex drive, reduced sperm concentration, feeling exhausted, **shrinking muscle mass**, and loss of bone density (osteoporosis).[9] High estrogen is associated with risk factors such as **weight gain or obesity, some tumors, liver diseases, and hypogonadism**.[9] Hypogonadism can **lower levels of estrogen, testosterone, and other hormones**, leading to many of the same symptoms of high estrogen levels, including **loss of muscle mass**; staying in shape can help keep estrogen levels low.[9]

Excess body fat is known to suppress testosterone production and cause hormonal imbalance in men. According to the health information website Healthline (USA), fat cells can convert testosterone into estrogen, further lowering testosterone levels. The article notes that low testosterone leads to muscle loss and difficulty in increasing muscle mass, especially in men with low testosterone. Thus, increased adipose tissue is linked with higher estrogen and lower testosterone, not with estrogen deficiency.

There is an association between obesity and low testosterone. Leptin, a hormone found in fat cells, is known to suppress testosterone production. Excess fat cells can also increase estrogen levels and thereby lower testosterone. Low testosterone, in turn, causes low libido, muscle loss, depressed mood, and low energy. This description links high fat mass to increased estrogen and reduced testosterone, rather than suggesting that high muscle mass causes estrogen deficiency.

Men with low estrogen levels have higher levels of internal (visceral) abdominal fat, which is known to increase the risk of cardiovascular disease, diabetes, and metabolic syndrome. In addition, men with estrogen deficiency have reduced bone strength and an increased risk of bone fractures. A fully grown male usually has an estradiol level of 10-40 picograms per milliliter (pg/ml).

The video explains that having a lot of muscle does not always mean that testosterone levels are high. Some men with large muscles have low testosterone levels because they built their muscles with improper methods such as using anabolic steroids, which can suppress endogenous male‑hormone production. It also notes that when abdominal fat and total body fat are high, the probability that male hormone is converted into female hormone increases. This discussion focuses on steroid use and obesity affecting testosterone and estrogen balance, rather than muscle mass itself causing estrogen deficiency.

The program states that among muscular men, there are quite a few whose testosterone is actually deficient because they increased their muscle mass in the wrong way, for example by using steroids, which can cause a decrease in male hormone. It also explains that as abdominal fat and total body fat increase, male hormone is more likely to be converted into female hormone. Thus, the issue is inappropriate training or drug use and high fat mass, not excessive muscle mass inherently causing estrogen deficiency.

Human studies in men show that testosterone is the principal hormone driving increases in muscle mass and strength, while estrogen in men is more closely linked to regulation of fat mass, bone health, and aspects of sexual function. There is no evidence that simply having high muscle mass in men directly causes estrogen deficiency; rather, estrogen levels in men depend mainly on testosterone levels and aromatase activity, which converts testosterone into estradiol. Some resistance-trained men can have normal or even higher estradiol levels because greater testosterone production provides more substrate for aromatization, illustrating that increased muscle mass is not inherently associated with estrogen deficiency.

Men with **high levels of estrogen may experience feminine fat distribution and reduced muscle mass**.[14] Additionally, **obesity can increase estrogen production in men** because body fat contains aromatase, leading to increased conversion of testosterone to estradiol.[14] The impact of obesity and increased estrogen levels in men is described as a **positive feedback loop**, where increased weight gain may result in increased estrogen, and increased estrogen can contribute to increased weight gain.[14]

The article on male hormones notes that when male hormone (testosterone) decreases, muscle mass and muscle strength fall, leading to a soft body and increased abdominal obesity; the arms and legs become thinner and the abdomen protrudes. Small movements cause easy fatigue, and depressive mood and decreased sexual function can occur. This clinical description shows that hormone deficiency in men leads to muscle loss and increased fat, not that high muscle mass itself causes estrogen deficiency.

The article on male health and estrogen dominance explains that even when testosterone levels are normal, high estrogen levels in men can lead to sexual dysfunction such as erectile problems. It describes "estrogen dominance" as a condition where estrogen is relatively high compared with testosterone and notes that diet and lifestyle factors can modify this balance. It does not claim that greater muscle mass causes estrogen deficiency; instead, it focuses on excess estrogen as a problem when unbalanced with androgens.

Therefore, estrogen is also part of the male secretion, but at an infinitesimal value under normal physiological conditions.[7] The article suggests that **building muscle stimulates the production of testosterone and testosterone counteracts the effects of estrogen**, claiming "testosterone and estrogen levels are interrelated (when one increases, the other decreases)."[7] It also notes that **testosterone is converted directly to estrogen in abdominal fat by the action of the enzyme aromatase**, and recommends reducing abdominal fat to lower estrogen.[7]