A 15-year-old girl is brought to the office for evaluation of short stature. The patient has always been short compared to her peers, but she recently tried out for her school's basketball team and now asks "if anything can make me taller." She has not yet undergone menarche and has never been sexually active. The patient takes no medications or oral contraceptives. Height is

Question

A 15-year-old girl is brought to the office for evaluation of short stature.  The patient has always been short compared to her peers, but she recently tried out for her school's basketball team and now asks "if anything can make me taller."  She has not yet undergone menarche and has never been sexually active.  The patient takes no medications or oral contraceptives.  Height is <3rd percentile and weight is at the 20th percentile.  Blood pressure is 130/80 mm Hg and pulse is 92/min.  Physical examination reveals clear lung fields and a 2/6 systolic ejection murmur heard loudest in the left infraclavicular area.  The abdomen is soft and nontender.  Breast development is Tanner stage 1, and pubic hair development is Tanner stage 4.  Which of the following laboratory values is most likely to be present in this patient?

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11ec25c8_d9e4_3055_bc81_c52f71f97d78_MD0003_00 This patient's short stature and primary amenorrhea are suggestive of Turner syndrome (TS). TS is a chromosomal abnormality caused by the complete or partial loss of an X chromosome (45,X). Additional clinical features of TS include webbed neck, broad chest with widely spaced nipples, and cubitus valgus (angling of forearms away from body). TS is associated with multiple cardiac abnormalities including aortic coarctation, identified by a systolic murmur at the left infraclavicular area and upper extremity hypertension. TS Almost all patients with TS have ovarian dysgenesis ("streak ovaries"), which causes primary ovarian insufficiency resulting in low estrogen and progesterone levels (Choice A). Estrogen is required for normal breast development (thelarche); therefore, patients with TS typically have minimal or no breast development. In addition, low estrogen levels cause a lack of negative feedback on the hypothalamic-pituitary-ovarian axis, which leads to elevated FSH and LH levels. Patients typically require estrogen replacement therapy to induce sexual development, improve growth/height, and increase bone mineral density. hypothalamic-pituitary-ovarian axis (Choice C) Inhibin A is released by the ovaries; therefore, levels are low in patients with TS. (Choice D) Elevated testosterone is seen in complete androgen insensitivity syndrome; patients are phenotypic women (46,XY karyotype) with primary amenorrhea, normal breast development, and absent pubic hair. In contrast, testosterone levels are low in patients with TS due to lack of production by the ovaries. (Choice E) Growth hormone (GH) deficiency can cause short stature and delayed puberty but is not associated with coarctation of the aorta. GH levels are typically normal in TS as short stature results from loss of X chromosome genes. GH therapy, however, is still recommended in patients with TS to improve height potential. (Choice F) Hypothalamic or pituitary etiologies of amenorrhea cause decreased LH levels. However, this patient's aortic coarctation makes TS more likely. Educational objective: Primary amenorrhea in patients with short stature and aortic coarctation is suggestive of Turner syndrome. Patients typically have ovarian dysgenesis (ie, primary ovarian insufficiency), which results in low estrogen levels. These low estrogen levels cause a lack of negative feedback on the hypothalamic-pituitary-ovarian axis, resulting in high FSH levels. References: Turner syndrome in girls presenting with coarctation of the aorta. (http://www.ncbi.nlm.nih.gov/pubmed/26323199) Clinical review: Turner syndrome: updating the paradigm of clinical care. (http://www.ncbi.nlm.nih.gov/pubmed/22472565)

A 15-Year-Old Girl Is Brought to the Office for Evaluation