hCG and Spermatogenesis: What the Research Measured

Why sperm production needs a signal from the brain

The pituitary gland releases two hormones that run the testes. LH tells the Leydig cells to make testosterone, and FSH supports the Sertoli cells that nurse developing sperm. Sperm production needs testosterone inside the testes at very high concentration: in one study of healthy men, intratesticular testosterone was about 1,174 nmol/L against about 14 nmol/L in blood.

When a man takes external testosterone, the brain senses plenty and turns LH and FSH down. In the same study, testosterone enanthate suppressed LH and FSH to about 5% and 3% of baseline, and testosterone inside the testes fell by 94%. A 2025 review describes the result plainly: exogenous androgens drastically reduce intratesticular testosterone and impair spermatogenesis.

What happened when hCG was added

hCG binds the LH receptor, so it can keep the Leydig cells working while LH is switched off. In the controlled study above, adding hCG to testosterone kept intratesticular testosterone in the normal range, and the level rose in step with the hCG given.

A clinical review of 26 men on testosterone therapy who also received hCG reported no change in semen parameters over more than a year of follow-up — volume, sperm density, motility and forward progression held steady — and no man became azoospermic (no sperm in the ejaculate).

Restoring sperm production: how long it took

In men whose pituitary does not make enough LH and FSH (hypogonadotropic hypogonadism), gonadotrophin therapy has been followed for years. In one centre, the median time to the first sperm in the ejaculate was about 5.5 months, to 5 million/mL about 12 months, and to 20 million/mL about 29 months. Conception occurred in 22 of 43 treatment courses.

A pooled analysis of four trials pre-treated men with hCG and then added FSH. Of 81 men still without sperm after hCG alone, 84% went on to produce sperm. Larger starting testicular volume and lower body-mass index predicted a better response — a reminder that FSH, not only LH activity, matters for the later stages.

Reading sperm parameters

Studies report semen parameters: volume, concentration (millions per mL), total count, motility (the share that move, and how well) and morphology (the share with a normal shape). The World Health Organization publishes reference ranges, and a 2012 analysis of the 2010 WHO update noted that the lower thresholds reclassified some men previously labelled abnormal.

A single result is a snapshot. Sperm take roughly three months to develop, so clinicians repeat tests before drawing conclusions.

The clinical route

If you are trying to conceive or think you may have a hormone problem, the right route is a fertility clinic or an endocrinologist. They test properly (semen analysis, LH, FSH, testosterone, oestradiol) and prescribe registered medicines under monitoring. Nothing here replaces that.