Testosterone is not the only cause of age–related changes in men

Symptoms often observed in middle-aged men, such as changes in the ratio of muscle and adipose tissue, a decrease in muscle strength and sexual function, are usually associated with a decrease in the production of the male sex hormone testosterone. However, the results of a study conducted by scientists at the Massachusetts General Practice Clinic, working under the guidance of Benjamin Z. Leder, indicate that the changes occurring in the male body are partly due to a decrease in the level of the female sex hormone estrogen.

Traditionally, the diagnosis of male hypogonadism – a decrease in the level of sex hormones accompanied by physical symptoms – is made based on the results of changes in the testosterone content in the blood. However, according to the authors, until now very little was known about what levels of testosterone are necessary to maintain certain body functions.

In addition to directly affecting a number of physical functions, a small proportion of testosterone in the male body under the action of the aromatase enzyme is converted into the female sex hormone estrogen. The higher the level of testosterone in the body, the greater its amount is converted into estrogen and vice versa. Therefore, it is not really clear which of these hormones is responsible for maintaining certain functions.

Two groups of men aged 20-50 years with normal reproductive function took part in the study devoted to the study of this issue. Initially, all participants received a drug that suppresses the production of all sex hormones. After that, the men of the first group were randomly divided into 5 subgroups, who received 4 different dosages of testosterone-containing gel or placebo daily for 16 weeks. Men of the second group received testosterone in the same dosages, as well as an aromatase inhibitor that suppresses the conversion of testosterone into estrogen. More than 150 men in each group completed the full cycle of the study. At the beginning and at the end of the study, the ratio of muscle and adipose tissue, as well as the strength of the leg muscles of the participants were evaluated.

Analysis of the results showed that the participants of the first group had a shift towards the accumulation of adipose tissue, by clinical standards corresponding to a mild testosterone deficiency. The reduction of fat-free body weight, thigh muscle volume and leg strength did not occur until the testosterone level decreased to sufficiently low values. At the same time, sexual desire progressively decreased throughout the entire period of decreasing testosterone levels, while erectile function was impaired only when it decreased to extremely low levels.

In participants treated with an aromatase inhibitor, an increase in the amount of body fat occurred regardless of testosterone levels. At the same time, suppression of estrogen synthesis had no effect on fat-free body weight, muscle volume and leg strength. At the same time, the negative effect on sexual function was more pronounced regardless of the level of testosterone in the blood.

In general, the results obtained indicate that testosterone levels affect fat-free body weight, as well as muscle volume and strength, while estrogen levels regulate the accumulation of fat in the body. Sexual function is provided by the action of both hormones.

To confirm the adequacy of the results obtained using the testosterone deficiency model developed by them, the authors plan to conduct a study involving elderly men. They believe that the appointment of hormone replacement therapy with testosterone, which has been quite popular in recent years, should be carried out on the basis of a set of symptoms, and not solely on the basis of the results of a blood test for testosterone content. Moreover, forms of testosterone that can be converted to estrogen under the action of aromatase should be used for therapy.

Article by Joel S. Finkelstein et al. Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men is published in the New England Journal of Medicine.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Massachusetts General Hospital:
Testosterone deficiency not the only cause of age-associated changes in men.

13.09.2013