Testosterone

Testosterone is not only known as the male hormone but is also a crucial biological component affecting overall health, metabolism, muscle and bone structure, sexual function, and mental performance. In this article, we examine testosterone from its production in the body to its physiological effects, based on scientific evidence.

What is Testosterone?

Testosterone is a steroid sex hormone. In men, it is primarily produced by the Leydig cells of the testes (95%) and to a lesser extent by the adrenal glands (5%). Its main precursor is cholesterol.

Testosterone Release According to Biorhythm

• Peaks between 08:00–10:00 in the morning.
• Decreases in the afternoon and evening.
• Seasonal variation: highest in summer, lowest in winter.

Morning serum testosterone measurements are recommended to avoid false negatives due to biorhythms.

Testosterone Across the Lifespan

• Fetal period: Production starts around the 8th week with testis development.
• Neonatal period: Short-term increase around the 6th month.
• Puberty: LH hormone stimulates a renewed rise in testosterone.
• 20–30s: Peak levels.
• After 50s: Gradual decline, potentially to 20–30% of peak.

Unlike menopause in women, testosterone production in men continues lifelong but gradually decreases.

Free vs. Bound Testosterone

Testosterone in blood exists in two main forms:

• ~3% free form – biologically active
• 50–60% bound to SHBG
• 30–40% weakly bound to albumin – can be released as needed

If total testosterone is low but free testosterone is normal, clinical interpretation can be misleading. SHBG levels should also be assessed.

Testosterone Metabolism in the Body

• Dihydrotestosterone (DHT) conversion → androgenic effects in target tissues like the prostate
• Conversion to estrogen → occurs in fat tissue, brain, and muscles
• Hepatic breakdown → metabolites excreted via bile and urine

Physiological Effects of Testosterone

Androgenic Effects

• Development of male secondary sexual characteristics (voice deepening, body hair, muscle mass)
• Growth spurt and male-type development during puberty

Reproductive Health

• Supports sperm production in the testes
• Direct effect on libido (sexual desire)

Anabolic Effects

• Muscle tissue development
• Bone mineral density and strength

Psychological and Emotional Effects

• Mood, self-confidence, motivation
• Behavioral regulation, impulsivity, aggression

Hematologic Effects

• Stimulates erythropoiesis in bone marrow
• Prevents anemia

Cardiometabolic Health

• Regulates lipid metabolism
• Balances HDL, LDL, and triglycerides
• Prevents visceral fat accumulation

Cognitive Functions

• Memory, focus, and overall mental performance
• Declining testosterone with age may contribute to cognitive deterioration

Implications of Low Testosterone

• Fatigue and low energy
• Reduced libido and erectile dysfunction
• Muscle loss and increased fat accumulation
• Difficulty concentrating
• Depressed mood
• Osteoporosis and bone pain
• Increased risk of insulin resistance and metabolic syndrome

When Should Testosterone Be Tested?

Blood tests should be taken in the morning (08:00–10:00, fasting) to measure:

• Total testosterone
• Free testosterone
• SHBG

Additional evaluations may include LH, FSH, and prolactin.

Testosterone: More Than a Sex Hormone

Testosterone is vital not only for sexual function but also for overall body systems. Its levels fluctuate based on age, season, stress, sleep, and metabolic health. Functional health approaches focus not just on hormone presence in blood, but also on systemic effects and hormonal balance.

LaraHealth Perspective

If you experience chronic fatigue, low libido, decreased muscle strength, or cognitive fog, comprehensive evaluation of your testosterone balance is crucial for long-term health. Feeling your best starts with hormonal balance.