genitourinary disorders
Male Hypogonadism
Diagnosis of Male Hypogonadism
Testing, beginning with follicle-stimulating hormone (FSH), luteinizing hormone (LH), andtestosteronelevels Congenital and childhood-onset hypogonadism are often suspected because of developmental abnormalities or delayed puberty. Adult-onset hypogonadism should be suspected on the basis of symptoms or signs but is easily missed because these clinical markers are insensitive and nonspecific. Klinefelter Syndrome (47,XXY) should be considered in adolescent males in whom puberty is delayed, young men with hypogonadism, and all adult men with very small testes. Hypogonadism requires confirmatory testing (see figure production is normal. The cause of hypogonadism is often evident clinically. Primary hypogonadism requires no further testing, although some clinicians do a karyotype to definitively diagnose Klinefelter Syndrome (47,XXY) . Total (and, when possible, free) serumtestosterone, serum FSH, and serum LH levels are measured simultaneously. The normal range for totaltestosteroneis 300 to 1000 ng/dL (10.5 to 35 nmol/L). Thetestosteronelevel should be drawn in the morning (before 10:00 AM) to confirm hypogonadism. Because of the increase in sex hormone–binding globulin (SHBG) with aging, totaltestosteronelevel is a less sensitive indicator of hypogonadism after age 50. Although serum freetestosteronemore accurately reflects functionaltestosteronelevels, its measurement requires equilibrium dialysis, which is technically difficult and not widely available. Some commercially available kits, including the analog freetestosteroneassay, attempt to measure serum freetestosteronelevels, but the results are often inaccurate, particularly in conditions (such as type 2 diabetes, obesity, and hypothyroidism) that alter SHBG levels. Freetestosteronelevels can be calculated based on SHBG,albumin, andtestosteronevalues; there are calculators available online. See theFree and Bioavailable Testosterone Calculator. Because of the pulsatile secretion of FSH and LH, these hormones are have been measured as a pooled sample of 3 venipunctures taken at 20-minute intervals, but these pooled samples seldom add clinically important information compared with a single blood sample. Serum FSH and LH levels are usually≤5 mIU/mL (5 IU/L) before puberty and between 5 and 15 mIU/mL (5 and 15 IU/L) in adulthood. 15 million sperm/mL, of which 50% are of normal morphology and are motile (see also Sperm Disorders ). * Totaltestosteronehas lower sensitivity for hypogonadism in men aged > 50 years. If the test for free and weakly boundtestosteroneis available, levels are measured. If not, levels are calculated. † Recommended by some physicians. CT=computed tomography; Fe=iron; FSH=follicle-stimulating hormone; GnRH=gonadotropin-releasing hormone; LH=luteinizing hormone; MRI=magnetic resonance imaging. Because any systemic illness can temporarily decrease levels oftestosterone, FSH, and LH, secondary hypogonadism should be confirmed by measuring these levels again at least 4 weeks after resolution of the systemic illness. To confirm secondary hypogonadism in adolescents, the GnRH stimulation test may be considered. If levels of FSH and LH increase in response to IV GnRH, puberty is simply delayed. If levels do not increase, true hypogonadism is likely. To help determine the cause of confirmed secondary hypogonadism, testing should include serum prolactin level (to screen for pituitary adenoma) and transferrin saturation (to screen for Hereditary Hemochromatosis ). Sella imaging with MRI or CT is done to exclude a pituitary macroadenoma or other mass in men with any of the following: Age<60 years with no other identified cause for hypogonadism Very low totaltestosteronelevels (<200 ng/dL [6.94 nmol/L]) Elevated prolactin levels Symptoms consistent with a pituitary tumor (eg, headache, visual symptoms) Also, if there are symptoms or signs of Cushing Syndrome , 24-hour urine collection for free cortisol or a 