Common Questions
What tests are used in diagnosing male hypogonadism?
A random total testosterone level is a reasonable screening test. If the level is definitively low (under 200 ng/dL), the diagnosis of hypogonadism is made. Using this level will miss men who would benefit from testosterone replacement (4) and some clinicians use 300 ng/dL as the cutoff value. Certain caveats are in order:
- In very obese men, changes in sex-steroid-binding globulin result in low total serum testosterone values. Under these circumstances, free testosterone levels should be tested (1), but only if it is measured by equilibrium dialysis, which is not widely available. Free testosterone levels measured by an analog method may be misleading.
- Marked diurnal variations in testosterone are present in young men, and this variation should be considered in interpreting testosterone levels (2, 3).
- If the initial value of total testosterone is borderline low, a more accurate value may be obtained by taking three repeat measurements, 15 to 20 minutes apart, and pooling the measurements for analysis, but this approach has not been validated.
Luteinizing hormone, drawn simultaneously with the testosterone level, documents whether hypogonadism is central (hypothalamic hypogonadism or pituitary insufficiency) or peripheral (primary testicular failure). Older men have an increased sensitivity to testosterone feedback so this is less accurate after age 50.
- Glass AR, Swerdloff RS, Bray GA; Dahms WT, Atkinson RL. Low serum testosterone and sex-hormone-binding-globulin in massively obese men. J Clin Endocrinol Metab 1977; 45(6): 1211-9.
- Bremner WJ, Vitiello MV, Prinz PN. Loss of circadian rhythmicity in blood testosterone levels with aging in normal men. J Clin Endocrinol Metab 1983; 56(6): 1278-81.
- Purifoy FE, Koopmans LH, Mayes DM. Age differences in serum androgen levels in normal adult males. Hum Biol 1981; 53(4): 499.
- Snyder PJ, Peachey H, Hannoush P, Berlin JA, Loh L, Holmes JH, et al. Effect of testosterone treatment on bone J Clin Endocrinol Metab. mineral density in men over 65 years of age 1999; 84(6): 1966-72.