LH and FSH: The Hormones That Actually Control Your Testosterone

When men think about testosterone, they usually think about the testes. That is where testosterone is made, after all. But the testes do not decide on their own how much to produce. They take signals from the brain, carried by two hormones most men have never heard of: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

Understanding how LH and FSH work gives you a different perspective on testosterone. Instead of focusing only on the end product, you can see the signaling chain and where it can break down.

The HPG Axis: Your Hormone Command Chain

The system that controls testosterone production is called the hypothalamic-pituitary-gonadal (HPG) axis. It is a three-level cascade that works somewhat like a thermostat for your reproductive hormones.

At the top sits the hypothalamus, a small region at the base of your brain. It releases gonadotropin-releasing hormone (GnRH) in pulses. GnRH travels a short distance to the anterior pituitary gland, where it stimulates cells called gonadotrophs to release two hormones: LH and FSH. These are the gonadotropins, the messengers that carry instructions from the brain to the gonads.

LH and FSH then travel through the bloodstream to the testes, where they act on different cell types.

LH: The Direct Trigger for Testosterone

Luteinizing hormone is the most direct hormonal driver of testosterone production. In adult men, LH binding to receptors on Leydig cells stimulates cAMP production and increases the movement of cholesterol into mitochondria, where it is converted step by step into testosterone.^[1]

This is why measuring LH alongside testosterone gives doctors useful information. In the European Male Ageing Study, low testosterone with low or normal LH was classified as secondary hypogonadism (a problem upstream of the testes), while low testosterone with elevated LH was classified as primary hypogonadism (the testes are not responding adequately). The study found that obesity was associated with the secondary type, and older age with primary and compensated types.^[3] Only a doctor can interpret these results for you.

FSH: The Fertility Hormone

While LH drives testosterone production, FSH has a different primary job: supporting sperm production. FSH regulates the proliferation and maturation of germ cells, on its own and together with LH, in the seminiferous tubules of the testes.^[2]

This distinction matters clinically. A man on exogenous testosterone (TRT) gets feedback signals that tell the brain enough testosterone is present. Exogenous testosterone suppresses intratesticular testosterone production and may lead to azoospermia or severe oligozoospermia, which is why TRT can impair fertility.^[4] If you may want children, discuss this with your doctor before considering any hormone therapy.

The Negative Feedback Loop

The HPG axis is a feedback system. When circulating testosterone and estradiol (which is made from testosterone by the aromatase enzyme) are high, they signal the hypothalamus and pituitary to dial down GnRH, LH, and FSH. When levels fall, the brake eases and LH and FSH rise. In men with obesity, a meta-analysis found that weight loss was associated with a decrease in estradiol, an increase in gonadotropins, and a rise in testosterone, consistent with this feedback being altered by excess body fat.^[7]

What Can Disrupt the HPG Axis

Obesity is associated with secondary hypogonadism: in the European Male Ageing Study, a BMI of 30 or higher was associated with a markedly higher relative risk of secondary hypogonadism.^[3] Weight loss in men with obesity is associated with higher testosterone, and the effect is larger with greater weight loss.^[7] More on this in our guide to body fat and testosterone.

Opioids are associated with lower testosterone. A systematic review and meta-analysis of 17 studies (2,769 participants) found significantly lower testosterone in men with regular opioid use compared with controls, regardless of opioid type, though the quality of evidence was low and the studies varied widely.^[8] If you take opioid medication and have symptoms of low testosterone, talk to the prescribing doctor; do not stop medication on your own.

Anabolic steroidsand other exogenous androgens can suppress the body's own testosterone production and sperm production.^[4]

Aging is associated with a gradual decline. In the Baltimore Longitudinal Study of Aging, which followed 890 men, total testosterone and free testosterone index declined with age independently of other measured health factors, and the proportion of men with hypogonadal levels increased with age.^[9] See our guide to testosterone levels by age.

Sleep matters because LH secretion in healthy men is augmented during sleep, with LH pulses occurring preferentially during non-REM sleep.^[10] In a crossover study of 35 healthy men, a night of total sleep deprivation reduced 24-hour testosterone secretion, especially in older men, and reduced morning LH, though overall LH was not detectably changed.^[5] The takeaway is that sleep matters for testosterone, but the mechanism is more complicated than lower LH alone. See sleep and testosterone.

Stress. Chronic stress is generally associated with lower testosterone, and stress hormones are thought to interact with the HPG axis, but the human evidence is mostly observational. See our guide on stress, cortisol, and testosterone.

Excessive exercise or major weight loss. A retrospective study of ten men with functional hypogonadotropic hypogonadism (after more than 10 hours per week of exercise or more than 10% weight loss) found low testosterone and LH, and five men who reduced exercise and gained weight normalized their testosterone.^[11] This is a reminder that very low energy availability can switch the axis down.

Habits That Support General Hormone Health

There is no proven way to raise LH on demand in healthy men. The habits below are not LH treatments; they are general-health behaviors associated with healthier hormone profiles in the studies above.

When Doctors Test LH and FSH Alongside Testosterone

If you have symptoms of low testosterone and your total testosterone comes back low, a doctor may order LH and FSH in follow-up testing to help understand why. Low testosterone with low or normal LH (secondary) points to causes upstream of the testes, such as obesity, medications, pituitary problems, or chronic illness. Low testosterone with elevated LH (primary) points to the testes themselves. The two situations are evaluated and managed differently, which is why you should not interpret hormone panels on your own.

A fuller panel may also include prolactin, estradiol, SHBG, and free testosterone, depending on your situation. Only a physician can decide which tests are appropriate.

The Bottom Line

Your testosterone level is the output of a signaling chain that starts in the hypothalamus, passes through the pituitary via LH and FSH, and ends at the testes. Every link can be affected by body weight, sleep, energy availability, medications, and age.

The practical message is not to chase LH numbers but to keep the foundations solid, and to ask a doctor to look at the whole picture if you have symptoms. This article is educational and not medical advice.

How Thrive Helps

Thrive helps you track the everyday habits associated with hormone health: sleep duration and quality, stress management, exercise, nutrition, and body composition. Each habit is graded by evidence strength so you can focus on what the science supports. Try Thrive free. Thrive is a wellness app and not a medical device; it cannot diagnose or treat hormone conditions.