The FSH, LH and testosterone blood tests evaluate male reproductive and hormonal function. FSH and LH are pituitary hormones regulating sperm production and testosterone secretion; testosterone is the principal male sex hormone. These tests help investigate infertility, low libido, erectile dysfunction, delayed or early puberty, and suspected hypogonadism or pituitary disease. Patterns distinguish primary (high FSH/LH, low testosterone) from secondary (low/normal FSH/LH, low testosterone) causes.

FSH, LH and prolactin are pituitary hormones affecting male reproduction. FSH stimulates Sertoli cells and supports sperm production; LH triggers Leydig cells to make testosterone, driving sexual development and sperm maturation. Prolactin has modulatory roles in reproductive and immune function; chronically high prolactin can suppress GnRH, lower testosterone, reduce libido and impair fertility.

For male fertility evaluation test: serum total testosterone (± free/sex‑hormone‑binding globulin if needed), luteinizing hormone (LH), follicle‑stimulating hormone (FSH), prolactin, estradiol, inhibin B, and thyroid function (TSH ± free T4). These identify testosterone deficiency, pituitary problems, impaired sperm production, and other endocrine causes of infertility. Your clinician will tailor tests based on history and semen analysis.

The tests are serum blood assays measuring follicle‑stimulating hormone (FSH), luteinizing hormone (LH) and prolactin levels. FSH and LH are often drawn on cycle day 2–4 to assess ovarian reserve and pituitary‑gonadal function; LH may also be measured mid‑cycle to confirm ovulation. Prolactin is measured in a morning fasting sample (avoid nipple stimulation) to evaluate amenorrhea, infertility, or suspected pituitary disease.

Luteinizing hormone (LH) is a pituitary hormone that stimulates testicular Leydig cells to produce testosterone, essential for sperm production and male fertility. Low LH can cause low testosterone and impaired spermatogenesis; high LH suggests primary testicular failure. Blood LH measurement helps diagnose infertility causes. Treatment may include hormone replacement or gonadotropin therapy to restore testosterone and spermatogenesis, depending on the cause.

A good testosterone level for male fertility is generally in the mid-normal adult range—roughly 400–800 ng/dL (14–28 nmol/L). Both very low and supraphysiologic levels (from exogenous testosterone) can impair sperm production. Free testosterone, normal LH/FSH and semen parameters also matter; fertility evaluation should include hormonal testing and a semen analysis to assess reproductive potential.