An 18-year-old patient presents to you for evaluation because she has not yet started her period. On physical examination, she is 5 ft 7 in tall. She has minimal breast development and no axillary or pubic hair. On pelvic examination, she has a normally developed vagina. A cervix is visible. The uterus is palpable, as are normal ovaries.
Which of the following is the best next step in the evaluation of this patient?
A. Draw her blood for a karyotypeThe evaluation and diagnosis of the patient with abnormal development of secondary sex characteristics is challenging as there are many potential causes. The evaluation of the patient should note the presence or absence of a uterus, breast buds, and pubic and axillary hair. Testicular feminization is a syndrome of androgen insensitivity in genetic males, characterized by a normal 46, X genotype, normal female phenotype during childhood, tall stature, and “normal” breast development with absence of axillary and pubic hair. Breast development (gynecomastia) occurs in these males because high levels of circulating testosterone (which cannot act at its receptor) are aromatized to estrogen, which then acts on the breast. The external genitalia develop as those of a female because testosterone cannot masculinize them, while the Müllerian structures are absent because of testicular secretion of MIF in utero. Gonadal dysgenesis (eg, 45, X Turner syndrome) is characterized by short stature and absence of pubertal development; in these girls the ovaries are either absent or streak gonads that are nonfunctional. In either case, estrogen production is possible, and therefore isosexual pubertal development does not occur. Kallmann syndrome (hypogonadotropic hypogonadism), the most likely diagnosis in this patient, should be suspected in an amenorrheic patient of normal stature with delayed or absent pubertal development, especially when associated with the classic finding of anosmia. Testing the sense of smell with coffee or perfume is a simple way to screen for this disorder. These individuals have a structural defect of the CNS involving the hypothalamus and the olfactory bulbs (located in close proximity to the hypothalamus) such that the hypothalamus does not secrete GnRH in normal pulsatile fashion, if at all. Other causes of minimal or absent pubertal development with normal stature include malnutrition; anorexia nervosa; severe systemic disease; and intensive athletic training, particularly ballet and running.