Testosterone Undecanoate

Endogenous androgens, mainly testosterone and dihydrotestosterone (DHT), are responsible for the normal growth and development of the male sex organs and for keeping up the secondary sex characteristics. They drive the growth and maturation of the prostate, seminal vesicles, penis and scrotum. They also shape male hair patterns (facial, pubic, chest and underarm hair), enlarge the larynx, thicken the vocal cords, and change body musculature and fat distribution.

Male hypogonadism is a clinical syndrome caused by insufficient secretion of testosterone, and it has two main causes. Primary hypogonadism comes from a fault in the gonads themselves, such as Klinefelter's Syndrome or Leydig cell aplasia. Secondary hypogonadism is different: the hypothalamus (or pituitary) fails to produce enough gonadotropins (FSH and LH).

Testosterone has a key role in male sexual differentiation and is also involved in regulating haematopoiesis, body composition and bone metabolism. So when a man with hypogonadism gets testosterone replacement therapy, he may see better sexual function, more lean body mass, higher bone density and better erythropoiesis, along with a larger prostate and changes in his lipid profile.

Testosterone is made by Leydig cells, and it works by binding to androgen receptors all over the body. It affects the voice, the genitals and mood, and it influences muscle growth and protein expression. This is why men with low testosterone often notice reduced libido, tiredness, mood swings and dysphoria. Exogenous testosterone is designed to copy the effects of the body's own testosterone.