The patient undergoes further evaluation with a pelvic ultrasound, which reveals a prepubertal uterus with small ovaries. Laboratory findings are as follows: Which of the following is the most likely underlying cause of the patient's condition?

Question

The patient undergoes further evaluation with a pelvic ultrasound, which reveals a prepubertal uterus with small ovaries.  Laboratory findings are as follows:  Which of the following is the most likely underlying cause of the patient's condition?

Quizplus · Accepted Answer

11ec25c8_d66f_c9d4_bc81_53cb7597bd88_MD0003_00 Turner syndrome (TS) is a sporadic chromosomal disorder caused by complete or partial deletion of an X chromosome. Absence of the second X chromosome results in gonadal dysgenesis (ie, poorly developed ovaries), which presents as "streak ovaries" (small ovaries with minimal or no follicles) on pelvic ultrasound. Due to loss of ovarian function (ie, primary ovarian insufficiency), patients with TS have low estrogen levels, resulting in primary amenorrhea and absent breast development. Low estrogen levels also inhibit negative feedback on the hypothalamic-pituitary-ovarian (HPO) axis, stimulating increased FSH and LH production. However, because TS does not affect the adrenal glands, normal adrenarche occurs and patients often develop pubic and axillary hair. hypothalamic-pituitary-ovarian (HPO) axis Diagnosis of TS is with karyotype analysis showing 45,XO. If karyotype is normal but suspicion for TS remains high, fluorescence in situ hybridization is performed to detect mosaicism (eg, 45,XO/46,XX) that is beyond the resolution of standard karyotyping. 45,XO (Choice A) The Müllerian duct develops into the uterus, fallopian tubes, and upper two-thirds of the vagina. Patients with abnormal development typically present with amenorrhea; however, uterine anomalies are seen on ultrasound. Ovarian development is not affected; therefore, FSH and LH levels are normal. (Choice C) Patients with androgen insensitivity syndrome (complete androgen receptor insensitivity) can have amenorrhea; however, they typically have tall stature and breast development (due to androgen conversion to estrogen). In addition, a uterus is not seen on ultrasound. (Choice D) Patients with congenital GnRH deficiency (ie, Kallmann syndrome) can have amenorrhea due to decreased hypothalamic stimulation of FSH and LH. (Choice E) Excess endogenous glucocorticoids (eg, Cushing syndrome) suppress GnRH, causing low FSH and LH levels. (Choice F) Functional hypothalamic amenorrhea occurs in adolescent girls with severe calorie restriction (eg, athletes, anorexia nervosa) due to suppression of the HPO axis. FSH and LH levels are low. Educational objective: Patients with Turner syndrome have primary amenorrhea and lack of breast development due to low estrogen levels associated with gonadal dysgenesis. Lack of feedback inhibition by estrogen on the hypothalamic-pituitary-ovarian axis results in increased FSH and LH. An absent X chromosome on karyotype analysis is diagnostic. References: Approach to the patient with Turner syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/20375216) FSH may be a useful tool to allow early diagnosis of Turner syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/29415703)

The Patient Undergoes Further Evaluation with a Pelvic Ultrasound, Which