What Causes Low T? 12 Causes, Including in Young Men

Modifiable Causes of Low Testosterone

1. Obesity and excess body fat — Adipose tissue contains aromatase, which converts testosterone to estradiol. Losing 10% of body weight can increase testosterone by 100+ ng/dL. Visceral fat is particularly problematic.
2. Sleep deprivation — Testosterone is produced primarily during sleep, with peak secretion during REM. Sleeping 5 hours instead of 8 reduces testosterone by 10-15% (JAMA, 2011). Sleep apnea further suppresses T through intermittent hypoxia.
3. Chronic psychological stress — Cortisol and testosterone have an inverse relationship. Chronic stress elevates cortisol, which suppresses GnRH at the hypothalamus, reducing LH and downstream testosterone production.
4. Alcohol consumption — Acute alcohol intake suppresses testosterone for 12-24 hours. Chronic heavy drinking causes testicular atrophy and liver dysfunction that impairs SHBG regulation.
5. Nutritional deficiencies — Zinc is required for testosterone synthesis; deficiency reduces T by up to 50% (Nutrition, 1996). Vitamin D deficiency, magnesium insufficiency, and low dietary fat intake also impair production. Certain foods and compounds may work in the opposite direction too — see our review of foods that may lower testosterone.
6. Endocrine disruptors — BPA (plastics), phthalates (fragrances/packaging), parabens (cosmetics), and pesticides have documented anti-androgenic effects. A 2014 meta-analysis in Environment International associated occupational pesticide exposure with 20% lower testosterone.

Medical Causes of Low Testosterone

7. Medications — Opioids (suppress GnRH; cause hypogonadism in 50-90% of chronic users), corticosteroids, ketoconazole, spironolactone, and some SSRIs reduce testosterone
8. Type 2 diabetes and insulin resistance — Insulin resistance reduces SHBG and total testosterone. Up to 50% of men with type 2 diabetes have low T (Diabetes Care, 2010)
9. Primary hypogonadism — Testicular causes: Klinefelter syndrome (47,XXY), undescended testes, testicular injury, mumps orchitis, or varicocele
10. Secondary hypogonadism — Pituitary or hypothalamic causes: pituitary adenoma, hemochromatosis (iron overload), head trauma, or anabolic steroid use (suppresses the HPG axis)
11. Overtraining — Excessive endurance exercise without adequate recovery suppresses testosterone. Marathon runners and triathletes commonly show low T levels
12. Aging — Total testosterone declines 1-2% per year after age 30, but healthy aging accounts for a smaller decline than lifestyle factors in most men

Distinguishing Primary from Secondary Hypogonadism

The distinction guides treatment:

Low Testosterone and Long-Term Health Risks

Beyond day-to-day symptoms, chronically low testosterone carries measurable long-term health consequences that make evaluation and treatment more than a quality-of-life issue.

Bone density and osteoporosis: Testosterone (partly through conversion to estradiol) supports bone mineral density in men. Men with prolonged low T are at increased risk of osteopenia and osteoporosis, and hypogonadism is a recognized secondary cause of fractures in men — a population where bone loss is often under-screened compared to women.

Cardiovascular risk: The relationship between testosterone and cardiovascular health is complex. Low testosterone is associated with adverse cardiometabolic markers — higher visceral fat, worse insulin sensitivity, and unfavorable lipid patterns — though this reflects an association with shared risk factors as much as direct causation. The TRAVERSE trial (2023), the largest randomized safety trial of TRT to date, found no increased cardiovascular event rate in hypogonadal men treated with testosterone over roughly three years of follow-up.

The TRT-and-prostate-cancer misconception: For decades, TRT was withheld from many hypogonadal men based on the belief that testosterone "feeds" prostate cancer. This concept originated from limited mid-20th-century observations, not rigorous trial data. Modern evidence — including large cohort studies and the Endocrine Society's 2018 clinical practice guideline — does not support the idea that testosterone therapy increases prostate cancer risk in men without pre-existing prostate malignancy. That said, monitoring PSA and performing appropriate prostate evaluation before and during TRT remains standard of care, since undiagnosed prostate cancer is a contraindication to starting treatment.

How to test testosterone at home

You don't need a lab appointment to check your own testosterone — a few at-home kits mail you a collection kit and return physician-reviewed results online within days:

Everlywell At-Home Testosterone Collection Kit for Men, Measures Total Testosterone Level for Accurate Results from CLIA-Certified Labs, Ages 18 Plus

Everlywell

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EqualDx 3-in-1 Androgen Test – at-Home Sample Collection Kit | Measure Total T, Free (Active) T & SHBG for Wellness Tracking | CLIA Lab Tested | Painless Collection

EqualDx

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Prefer to order direct? The Everlywell Testosterone Test uses a CLIA-certified lab, physician-reviewed results, and prepaid return shipping.