Adolescent Development, testicular feminization
Most teens have menarche within 2 to 2.5 years after thelarche or within 1 year of attaining full physical maturity. The presence of primary amenorrhea and normal secondary sexual characteristics at age 17 in the otherwise healthy adolescent girl described in the vignette warrant further evaluation.
There are numerous causes of primary amenorrhea, but not all need to be considered in a patient who has mature secondary sexual characteristics. Although her external genitalia are phenotypically female, the presence of a blind vaginal pouch is most consistent with the diagnosis of male pseudohermaphroditism. A serum karyotype will confirm this diagnosis.
Complete testicular feminization is the most common cause of male pseudohermaphroditism (phenotypic female who has 46,XY karyotype and with testes) and results from androgen insensitivity. Not all affected individuals present with ambiguous genitalia because the spectrum of sensitivity is broad. If the receptor to androgens is nonfunctional or absent, the external genitalia will be those of a normal female. The diagnosis is usually delayed until the absence of menses brings the adolescent to medical attention. Internal female genitalia do not form because the müllerian ducts regress under the effects of müllerian inhibiting factor produced by occult male gonads located in the abdomen. However, low levels of gonadal and adrenal estrogens, unopposed by androgens, allow breast development to occur in affected individuals.
Signs and symptoms of male pseudohermaphroditism are variable, depending on the etiology. As described previously, the phenotypic female may present with primary amenorrhea or an infant may have ambiguous genitalia noted at birth. The otherwise healthy teenager who has androgen insensitivity may have sparse axillary and pubic hair, normal breast development, and a blind vaginal pouch with absence of the ovaries, uterus, and fallopian tubes. Testes and normal male levels of testosterone are present.
Because the adolescent described in the vignette does not have a central cause of amenorrhea, computed tomography of the head is unnecessary. Furthermore, magnetic resonance imaging is the study of choice to visualize the pituitary gland. Computed tomography of the pelvis may confirm the absence of internal female genitalia, but will not make the diagnosis. A serum estradiol level is unnecessary in the adolescent who has mature breast development. A serum prolactin level is also not indicated because the primary amenorrhea clearly stems from abnormal genital anatomy.
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