Testosterons

Testosterone is a steroid hormone of the androgen class and the principal male sex hormone in humans. It is primarily produced in the testes by Leydig cells, with smaller contributions from the adrenal glands; in women, ovaries and adrenal glands produce testosterone in much lower amounts. Testosterone influences the development of male reproductive tissues during fetal and postnatal life and drives the appearance of secondary sexual characteristics at puberty, while also affecting other tissues in both sexes.

Production and regulation: It is synthesized from cholesterol through a series of enzymatic steps. Its release is regulated by the hypothalamic-pituitary-gonadal axis: gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates luteinizing hormone (LH) release from the pituitary, which in turn stimulates testosterone production in the testes. Follicle-stimulating hormone (FSH) supports sperm production. Testosterone levels show a diurnal rhythm and can decline with age.

Functions: In puberty it promotes sperm production, genital development, and secondary sexual characteristics (facial and body hair, deepening voice). In adults it supports muscle mass, bone density, red blood cell production, libido, mood, and energy. In women, testosterone contributes to libido and overall well-being at low levels.

Clinical aspects: Low testosterone (hypogonadism) may be treated with testosterone replacement therapy (TRT) delivered by injections, gels, patches, or implants. TRT can improve symptoms but may cause adverse effects such as acne, erythrocytosis, sleep apnea, prostate changes, and reduced fertility. Testosterone use as a performance enhancer is banned in most sports and can cause health risks. Monitoring includes blood tests and assessment of symptoms.