Syndromes of Hypogonadotropic Hypogonadism
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Short for Prepubertal, later Prepubertal, Prepubertal, Low for Normal Normal delay in chronologic pubertal later pubertal later normal chronologic growth and age, usually age, adolescence appropriate for
From Grumbach MM, Styne DM: Puberty. In Wilson JD, Foster DW, editors: Williams Textbook of Endocrinology, ed 9, Philadelphia, 1997, WB Saunders. DHEAS, Dehydroepiandrosterone sulfate; GnRH, gonadotropin-releasing hormone; LH, luteinizing hormone.
Decreased gonadotropin function occurs when voluntary Hypergonadotropic Hypogonadism dieting, malnutrition, or chronic disease results in weight lossto less than 80% of ideal weight. Anorexia nervosa is charac-
Available @ StudentConsult.com terized by striking weight loss and psychiatric disorders (seeChapter 70). Primary or secondary amenorrhea frequently is found in affected girls, and pubertal development is absent orminimal, depending on the level of weight loss and the age atonset. Regaining weight to the ideal level may not immediately reverse the condition. Increased physical activity, evenwithout weight loss, can lead to decreased menstrual frequency and gonadotropin deficiency in athletic amenorrhea; when physical activity is interrupted, menstrual function mayreturn. Chronic or systemic illness (e.g., cystic fibrosis, diabetes mellitus, inflammatory bowel disease, or hematologicdiseases) can lead to pubertal delay or to amenorrhea fromhypothalamic dysfunction. Hypothyroidism inhibits the onset of puberty and delays menstrual periods. Converselysevere primary hypothyroidism may lead to precociouspuberty.
Hypergonadotropic hypogonadism is characterized by elevated gonadotropins and low sex steroid levels resulting from primary gonadal failure. This permanent condition is almost always diagnosed following the lack of entry into gonadarche and is not suspected throughout childhood. Gonadotropins do not increase to greater than normal until shortly before or around the normal time of puberty.
Ovarian failure is diagnosed by elevated gonadotropins. Turner syndrome, the syndrome of gonadal dysgenesis, is a common cause of ovarian failure and short stature. The karyotype is classically 45,XO, but other abnormalities of the X chromosome or mosaicism are possible. The incidence of Turner syndrome is 1 in 2000 to 1 in 3000 births. The features of a girl with Turner syndrome need not be evident on physical examination or by history. The diagnosis must be considered in any girl who is short without a contributory history. Patients with other types of gonadal dysgenesis and galactosemia as well as patients treated undergoing radiation therapy or chemotherapy for malignancy may develop ovarian failure.
Klinefelter syndrome (seminiferous tubular dysgenesis) isthe most common cause of testicular failure. The karyotype is47,XXY, but variants with more X chromosomes are possible. Theincidence is approximately 1 in 500 to 1 in 1000 in males. Testosterone levels may be close to normal, at least until mid-puberty,because Leydig cell function may be spared; however seminiferous tubular function characteristically is lost, causing infertility.Commonly LH levels may be normal to elevated, whereas FSHlevels are usually more unequivocally elevated. The age of onsetof puberty is usually normal, but secondary sexual changes maynot progress because of inadequate Leydig cell function.
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