Impaired muscle and beard development

Impaired muscle and beard development means the loss or reduction of muscle mass or facial hair. 

Muscle

The gender divergence in the bone-muscle relationship becomes strongly evident during adolescence. 

In females, growth is characterized by increased estrogen levels and increased mass and strength of bone relative to that of muscle, whereas in men (Pic. 1), increases in testosterone fuel large increases in muscle, resulting in muscle forces that coincide with a large growth in bone dimensions and strength. 

In adulthood, significant age-related losses are observed for muscle tissues. Large decrease in estrogen levels in women appears to diminish the skeleton's responsiveness to exercise more than in men. In contrast, the aging of the muscle-bone axis in men is a function of age related declines in both hormones.

Men with low free testosterone levels are more likely to develop mobility limitation and experience increase in mobility limitation compared to men with normal testosterone levels. 

Beard

Beard development (Pic. 2) is controlled by testosterone. If the level dropped, man will experince the loss of facial hair.

Reduction of body mass and beard is associated with two diagnoses which strictly affect fertility. There two diagnoses are Klinefelter syndrome and hypogonadism.

Klinefelter syndrome

The term Klinefelter syndrome (KS) describes a group of chromosomal disorders in which there is at least one extra X chromosome to a normal male karyotype, 46,XY. Some males with Klinefelter syndrome have the extra X chromosome only in some of their cells (mosaic Klinefelter syndrome). Man suffering from Klinefelter syndrome has significantly lower level of testosterone, which mai lead to muscle and beard loss.

Although most patients with Klinefelter syndrome are infertile, there have been a few patients with reports of pregnancy without assisted medical technology, typically in mosaic cases. With the introduction of intracytoplasmic sperm injection, which involves the use of sperm extraction from deep within the testicles of patients with non-mosaic Klinefelter syndrome, some XXY men will have an increased chance of fathering a child. 

Hypogonadism

Hypogonadism means diminished functional activity of the gonads which are the testes in males due to disease of brain or the testicles itself. The main purpose of testicles is to produce sperms under the control of testosterone.

Low testosterone levels impair muscle and beard development, but more severe is that it can lead to reduced sperm production (oligospermia), decreased libido and sexual satisfaction, and strength of erections in men.