Testosterone Effects

Products

Testosterone is commercially available as a drug product including transdermal gel, transdermal patch, transdermal solution, and injectable. In some countries, other dosage forms such as buccal tablets are available. Andriol Testocaps capsules have been discontinued in many countries since 2020.

Structure and properties

Testosterone (C19H28O2, Mr = 288.4 g/mol) is a steroid. It exists as a white crystalline powder or as colorless to yellowish white crystals and is practically insoluble in water. In some cases, ester derivatives and prodrugs such as testosterone undecanoate or testosterone anthate are also contained in drugs. Testosterone undecanoate, for example, is an ester of testosterone with undecanoic acid, a C11 fatty acid. In testosterone anthate, the it is esterified with enanthic acid, a C7 fatty acid. In this case, the active ingredient is formed by cleavage of the side chain.

Effects

Testosterone (ATC G03BA03) has anabolic and androgenic properties and is formed primarily in the Leydig cells of the testis from cholesterol. It leads to the expression and maintenance of male sexual organs and characteristics. Testosterone has numerous functions in the body and affects the skin, muscles, skeleton, bone marrow, liver, kidneys and central nervous system, among others. It is also necessary for libido and for sperm formation and fertility. The effects are due to interaction with androgen receptors, which affect gene expression. In hypogonadism, testosterone replaces the missing androgen in the bloodstream and ensures physiological concentrations. Testosterone has low oral bioavailability and is therefore often administered bypassing the digestive tract. When ingested, only a small fraction enters the systemic circulation. The half-life is approximately 24 hours. The endogenous production of testosterone is regulated by the central nervous system. Gonadotropin-releasing hormone (GnRH) from the hypothalamus leads to the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the anterior pituitary. LH and FSH promote testosterone formation and secretion, and FSH promotes spermatogenesis.

Indications

  • Hypogonadism in men (hormone replacement therapy, TRT, Testosterone Replacement Therapy).
  • Puberty induction in pubertas tarda in boys (delayed onset puberty).

Off-label, testosterone is also used for a so-called sex change in women.

Dosage

According to the SmPC. Testosterone is administered perorally, buccally, intramuscularly, nasally, or transdermally, depending on the drug. Capsules are taken with food.

Abuse

Testosterone supplements are abused as doping agents for sports, bodybuilding, and physical attractiveness enhancement. Because of the potential adverse effects, abuse is not advised. See also under the articles Anabolic steroids and Doping agents.

Contraindications

  • Hypersensitivity
  • Treatment of women
  • Pregnancy
  • Prostate cancer
  • Breast cancer
  • Liver tumors in patient history
  • Hypercalcemia associated with a malignant tumor

For complete precautions, see the drug label.

Interactions

Testosterone is a substrate of CYP isoenzymes. Corresponding drug interactions with CYP inhibitors and inducers are possible. Other interactions have been described with oral anticoagulants (vitamin K antagonists), glucocorticoids, and with antidiabetic agents.

Adverse effects

The most common possible adverse effects include acne, chest pain, muscle pain, prostate enlargement, hot flashes, weight gain, and administration site reactions. Testosterone may impair fertility by suppressing spermatogenesis. This is due to inhibition of follicle-stimulating hormone (FSH) release in the pituitary gland. When exogenous testosterone is supplied, the body’s own production and secretion is suppressed. This is due to a negative feedback loop at the level of the pituitary and hypothalamus. Exogenous testosterone inhibits the formation of the endogenous hormone in the testes, which promotes sperm formation.Testosterone therefore acts like a contraceptive (contraceptive) for men, but is less reliable than “the pill” for women.