Review Question - QID 101663

The clinical presentation is consistent with Klinefelter syndrome, which is characterized by elevated aromatase.

Klinefelter syndrome is caused by a karyotype of two or more X chromosomes due to nondisjunction or translocation during meiosis. Patients with Klinefelter syndrome have decreased testosterone levels due to Leydig cell dysfunction. Loss of Sertoli cells also occurs, and leads to decreased levels of inhibin. Plasma gonadotropin levels increase due to a lack of negative feedback. The increase in serum follicle stimulating hormone (FSH) up-regulates aromatase, which leads to increased conversion of testosterone to estrogen. The estrogen:testosterone ratio is highly correlated to the degree of feminization in patients with Klinefelter syndrome.

Wattendorf et al. review Klinefelter syndrome and report the following: (1) Approximately one in 1,000 boys is born with an additional X chromosome—47,XXY, the karyotype that causes Klinefelter syndrome, (2) the Klinefelter karyotype is detected at or before birth in 10 percent of affected boys, and it is found during adulthood in 25 percent of affected men and (3) almost all men with a 47,XXY karyotype will be infertile; Klinefelter syndrome accounts for 3 percent of male infertility.

Paduch et al. review the epidemiology, pathophysiology, and treatment options for Klinefelters syndrome and associated infertility. They report treatment with aromatase inhibitors can lower intra-testicular estradiol levels and have beneficial effects on testosterone production and spermatogenesis in men with Klinefelter syndrome.

Illustration A is a clinical photo that shows the characteristic features of Klinefelter syndrome. Notice the clinical features of hypogonadism, long extremities, shrunken testicles and testicular atrophy, gynecomastia, and female hair distribution. Illustration B is a karyotype of someone with Klinefelter. Notice the additional X chromosome.

Incorrect Answers:
Answer 1: Leydig cell dysfunction leads to decreased levels of testosterone in Klinefelter’s syndrome.
Answer 2: A loss of Sertoli cells in Klinefelter’s syndrome leads to decreased levels of inhibin.
Answer 4: Azoospermia (lack of ejaculatory sperm) is a common reason for infertility in patients with Klinefelter’s syndrome.
Answer 5: Malformation of seminiferous tubules in Klinefelter’s syndrome leads to a general loss of Sertoli cells in afflicted patients.