Dysfunction of hormonal production by testes (hypogonadism)

The LH/FSH ratio compares levels of luteinizing hormone to follicle-stimulating hormone, both produced by the pituitary gland. While FSH stimulates egg follicle development in the ovaries, LH triggers ovulation and supports progesterone production. The ratio between these hormones provides crucial insights into ovarian function and reproductive health that neither hormone alone can reveal.

Luteinizing hormone (LH) is produced by the pituitary gland in the brain. In women, it triggers ovulation and supports estrogen and progesterone production, while in men it stimulates the testes to produce testosterone.

FSH (Follicle Stimulating Hormone) is a pituitary hormone that stimulates egg development in ovaries and sperm production in testes. FSH levels vary throughout the menstrual cycle, surge during ovulation, and rise drastically after menopause when ovaries stop responding.

Testosterone and estradiol work in balance. In men, a small share of testosterone is continuously converted into estradiol, the main estrogen, by the enzyme aromatase, which is most active in fat tissue. The T:E2 ratio compares the two hormones and shows how strongly this conversion is running. A low ratio means relatively more estradiol. Common drivers are excess body fat, regular alcohol use, reduced liver clearance and low testosterone production itself. In men this pattern can contribute to reduced libido, difficulty building muscle, fatigue, mood changes and breast tissue growth. A high ratio points to too little estradiol relative to testosterone, which matters for bone strength, joints and sexual function even when testosterone itself looks fine. Body fat, alcohol, sleep and training all influence the ratio, so it often improves with the same habits that support healthy testosterone. We calculate it from testosterone and estradiol measured in the same molar unit (pmol/l). Ranges quoted in US units (ng/dL divided by pg/mL) are roughly 9 times lower than values on this scale.

FAI estimates the amount of active testosterone in the blood relative to binding proteins.

The primary male sex hormone responsible for sexual development, sperm production, muscle mass maintenance, bone density, and overall energy levels. Low levels can cause fatigue, reduced libido, erectile dysfunction, decreased muscle mass, and mood changes. Age-related decline is normal, but significant deficiency may warrant supplementation.

A glycoprotein that regulates hormone bioavailability by binding to sex hormones in circulation. SHBG levels influence the amount of active hormones available to tissues and can reflect metabolic and endocrine health.

The unbound, biologically active fraction of total testosterone that can interact with cellular receptors. This measurement provides insight into androgenic activity affecting metabolism, body composition, and various physiological functions. In this panel it is a calculated value: rather than being measured directly, it is derived from total testosterone, SHBG and albumin using the Vermeulen equation (the laboratory reference method is equilibrium dialysis). Because the calculation corrects for SHBG, free testosterone is the guideline-preferred measure of androgen status when SHBG is abnormal or total testosterone sits near the lower limit of normal, and it is more sensitive than total testosterone for detecting male hypogonadism and female androgen excess such as PCOS.

The primary active estrogen in the body. Estradiol is produced in the gonads (ovaries and testes) and in adipose tissue. It plays a central role in bone metabolism, cardiovascular protection, brain function, mood regulation, and reproductive health. Levels vary with the menstrual cycle and decline significantly during menopause. Low levels are associated with reduced bone density, mood disturbances, and impaired fertility. Elevated levels may indicate hormonal imbalance or increased aromatase activity.