Men with androgen deficiency may have symptoms that include decreased libido, impaired erectile function, decreased body and facial hair, easy fatigability, decreased muscle mass and strength, increased body fat, bone pain or fractures resulting from low
From: Male Hypogonadism: Basic, Clinical, and Therapeutic Principles Edited by: S. J. Winters © Humana Press Inc., Totowa, NJ
aBased on a reference range of serum T levels of between 300 to 1000 ng/dL
Fig. 1. Who should be treated with androgen replacement therapy?
bone mineral density (BMD), and increased negative mood parameters, such as irritability, nervousness, inability to concentrate, and poor quality of life. Many of these symptoms are also observed in aging men.
For confirmation of the diagnosis of male hypogonadism, the total serum testosterone testosterone level should be measured, preferably in the morning, because of the known diurnal variation of serum testosterone concentrations. It should be noted that some clinical laboratories use testosterone assays with testosterone or a testosterone analog as the assay standard, using chemiluminence methods on automated platforms (5). These newer assays might give a testosterone reference range for adult men, which is quite different from those obtained using traditional radioimmunoassays. The clinician must carefully review the reference range quoted by each laboratory to accurately diagnose hypogonadism (5). The reference range generally is based on serum values from healthy young adult men. Serum total testosterone assays in which the reference ranges differ from approx 300-1000 ng/dL may be suspect. Based on a reference range of serum testosterone levels in healthy adult young men of 300 to 1000 ng/dL, if the serum testosterone level is less than 250 ng/dL, the patient is most likely hypogonadal. Causes for the hypogonadism should be identified, and the patient should be considered for androgen replacement therapy (see Fig. 1). If the serum testosterone exceeds 350 ng/mL, the patient is not biochemically hypogonadal. Other causes of his symptoms should be investigated. If a total serum testosterone level is in the lower normal or slightly below the normal range (250 to 350 ng/dL), a repeat morning serum testosterone level, together with a measurement of free or bioavailable testosterone may be helpful (6-9). The free testosterone should be measured by equilibrium dialysis (9), or the level of sex hormone-binding globulin (SHBG) should be measured to calculate the free testosterone according to an established formula (10). Most clinical laboratories currently measure serum free testosterone using analog displacement assays on automated platforms with chemiluminescent-labeled reagents. Such assays of free testosterone do not accurately assess the free testosterone fraction, and are not recommended (11,12). Bioavailable testosterone (non-SHBG testosterone) is the fraction of testosterone in the serum that is free and albumin (Alb) bound. This is usually measured after ammonium sulfate treatment of the serum. The SHBG-bound hormone is in the precipitate, and the supernatant contains the free and Alb-bound fraction (7-8). Assays for bioavailable testosterone are not available in many laboratories, and reference ranges have to be established by each laboratory. If the repeat morning serum testosterone levels or the serum free testosterone or bioavailable testosterone levels are below the reference range of the laboratory, the patient may be considered for testosterone replacement therapy. The finding of an elevated serum luteinizing hormone (LH) level established the diagnosis of primary testicular hypogonadism in men with borderline low serum testosterone levels. Patients with functional or structural etiologies for hypogonadotropic hypogonadism will have low or inappropriately normal serum LH concentration coupled with low serum testosterone.
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