Normal Testosterone, FSH, and LH Levels in Adult Males
Normal Testosterone Reference Ranges
The normal range for total testosterone in adult men is 300-800 ng/dL in most laboratories, though this represents a general consensus rather than a standardized value. 1
Age-Specific Testosterone Considerations
- Young men (20-44 years) have higher testosterone levels than older men and should be evaluated with age-specific cutoffs rather than the traditional 300 ng/dL threshold. 2
- For men in their 20s, the middle tertile (normal range) is approximately 409-575 ng/dL 2
- For men in their 30s, the middle tertile is approximately 350-498 ng/dL 2
- For men in their 40s, the 2.5th-97.5th percentile range is 251-914 ng/dL (8.7-31.7 nmol/L) 3
- For men in their 50s, the range is 216-876 ng/dL (7.5-30.4 nmol/L) 3
- For men in their 60s, the range is 196-859 ng/dL (6.8-29.8 nmol/L) 3
- For men in their 70s, the range is 156-818 ng/dL (5.4-28.4 nmol/L) 3
Critical Measurement Considerations
- Morning measurements (between 8-10 AM) are essential, as testosterone levels naturally fluctuate throughout the day with highest levels occurring in the morning. 1, 4
- Two separate fasting morning testosterone measurements should be obtained to confirm hypogonadism, as single measurements are insufficient due to assay variability 5
- Free testosterone measurement by equilibrium dialysis is essential when evaluating borderline total testosterone levels, particularly in men with obesity or diabetes where low sex hormone-binding globulin may artificially lower total testosterone 5
Important Laboratory Variability
- Reference ranges for testosterone vary significantly among laboratories, with lower limits ranging from 130-450 ng/dL (a 350% difference) and upper limits ranging from 486-1,593 ng/dL (a 325% difference). 6
- The mean lower reference value across 120 U.S. laboratories is 231 ± 46 ng/dL (range 160-300 ng/dL) 7
- The mean upper reference value is 850 ± 141 ng/dL (range 726-1,130 ng/dL) 7
- Only 9% of laboratories create reference ranges unique to their region; most validate instrument-recommended values with limited internal samples 7
Normal FSH and LH Levels
Serum LH and FSH concentrations should be measured when testosterone levels are confirmed to be low, to distinguish primary (testicular) from secondary (pituitary-hypothalamic) hypogonadism. 4
Interpretation of Gonadotropin Levels
- Elevated LH/FSH with low testosterone indicates primary (testicular) hypogonadism 4
- Low or low-normal LH/FSH with low testosterone indicates secondary (hypothalamic-pituitary) hypogonadism 4
- In men with hypogonadotropic hypogonadism, baseline FSH levels average approximately 2.8 IU/L and LH levels average approximately 2.3 IU/L before testosterone replacement 8
- During testosterone replacement therapy in men with secondary hypogonadism, FSH typically suppresses to approximately 1.1 IU/L and LH to approximately 0.8 IU/L 8
Clinical Significance
- The pituitary-testicular hormonal axis maintains physiological negative feedback between testosterone and gonadotropins even in men with hypothalamic-pituitary disease 8
- Higher gonadotropin levels during testosterone replacement significantly decrease the chance of achieving normal testosterone levels (eugonadism) 8
- Gonadotropin levels categorized as low (<0.5 IU/L), medium (0.5-2 IU/L), or high (>2 IU/L) can help assess adequacy of androgen replacement 8
Common Pitfalls in Testosterone Assessment
- Up to 25% of men who receive testosterone therapy do not meet the criteria to be diagnosed as testosterone deficient, highlighting the importance of proper diagnosis before starting treatment. 5
- Nearly half of men placed on testosterone therapy do not have their testosterone levels checked after therapy commences 5
- Approximately 20% of men who had their testosterone level measured before initiating therapy had a level above 300 ng/dL 5
- Many laboratories use poorly defined and variable reference values based on limited population studies of men with unknown medical and reproductive histories 7