Male Hypogonadism

Male hypogonadism is defined as "inadequate gonadal function" manifested by deficiency in gametogenesis or secretion of gonadal hormones. Primary hypogonadism is caused by dysfunction in the testes from either chromosomal or acquired disorders (Box 35-8). Secondary hypogonadism is caused by an abnormality of the hypothalamic-pituitary axis. Males may present with infertility, decreased testicular size, changes in libido, impotency, gynecomastia, delayed puberty, or a combination of these (Swerdloff and Wang, 2004).

Diagnosis

Clinical diagnosis again begins with history, including information about sexual developmental milestones, current symptoms, ambiguous genitalia at birth, cryptorchidism, behavioral abnormalities, anosmia, surgeries, sexually transmitted diseases (STDs), and medications. History should include the presence of acute and chronic medical conditions and neurologic symptoms. Physical examination is directed toward sexual characteristics, body habitus, gyne-comastia, and signs of hypogonadism. Testis should be measured for length and width with an orchidometer. Consistency of the testes should be noted and a scrotal examination done for the presence of varicocele. A nonpalpable prostate may imply testosterone deficiency. A low morning (8-10 am) serum testosterone level confirms hypogonadism. Serum LH and FSH levels are elevated in primary hypogo-nadism and are normal to low in secondary hypogonadism. Semen analysis will assess the capability of spermatogenesis. An increase in sex hormone-binding globulin (SHBG) may imply hyperthyroidism, severe androgen deficiency, liver disease, or estrogen excess. A low level of SHBG may indicate hypothyroidism, polycystic ovary syndrome (PCOS), obesity, or acromegaly. Prolactin level should be measured to identify a prolactinoma, followed by CT or MRI, if elevated. Other studies, such as bone mineral density (BMD), pituitary imaging, genetic studies, and in some cases testicular biopsy, may be indicated.

Klinefelter's syndrome is the most common genetic cause of male infertility. It is caused by a chromosomal aberration, most often 47,XXY. Phenotypic males can present with small firm testicles, infertility, tall height, long legs, gynecomastia, and varying symptoms of androgen deficiency and undervir-ilization. Treatment is replacement of testosterone to prevent the sequelae of androgen deficiency.

Kallmann syndrome is an inherited disorder (see Pituitary Disorders). The most common form is isolated gonadotro-pin deficiency caused by defective GnRH secretion from the hypothalamus. Patients with Kallmann syndrome usually come to medical attention because of delayed puberty or incomplete sexual development. Anosmia or hyposmia is present in 80% of patients (remember the coffee grounds everyone carried around in medical school?) and establishes

Box 35-8 Causes of Hypogonadotropic Hypogonadism (HH)

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