A 38-year-old woman is seen by a gynecologist on a routine visit. A complete history is taken and is non-contributory except for the fact that the patient’s menstrual irregularities apparently developed insidiously over the preceding decade. Screening physical examination is performed. Routine serum chemistries and complete blood count are sent, as are Pap smear studies. Pelvic ultrasound studies are also performed. Pregnancy test is negative. Endometrial biopsy shows proliferative endometrium. All other results are within normal limits, except for evidence of a mild iron deficiency anemia. Which of the following is the most likely diagnosis?

**Core Concept**
The patient's menstrual irregularities, coupled with the presence of proliferative endometrium on endometrial biopsy, suggest a condition characterized by anovulatory cycles, leading to unopposed estrogen action on the endometrium. This scenario is typical of a common endocrine disorder affecting women of reproductive age.

**Why the Correct Answer is Right**
The patient's symptoms and laboratory findings are consistent with Polycystic Ovary Syndrome (PCOS). PCOS is characterized by chronic anovulation, resulting in estrogen dominance and unopposed estrogen action on the endometrium. This leads to the development of proliferative endometrium, which is not consistent with the patient's amenorrhea. The presence of mild iron deficiency anemia is also common in PCOS due to menstrual irregularities and decreased iron stores. The pelvic ultrasound studies may show multiple small follicles in the ovaries, a characteristic feature of PCOS.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the patient's proliferative endometrium on endometrial biopsy. A diagnosis of Asherman's syndrome would typically be associated with atrophic or scarred endometrium, not proliferative endometrium.

**Option B:** This option is incorrect because it does not explain the patient's menstrual irregularities and proliferative endometrium. A diagnosis of thyroid disorders, such as hypothyroidism, may be associated with menstrual irregularities, but it would not typically result in proliferative endometrium.

**Option C:** This option is incorrect because it does not account for the patient's pelvic ultrasound findings or the presence of proliferative endometrium. A diagnosis of ovarian cancer would not typically present with proliferative endometrium on endometrial biopsy.

**Option D:** This option is incorrect because it does not explain the patient's menstrual irregularities or the presence of proliferative endometrium. A diagnosis of premature ovarian failure (POF) would typically be associated with amenorrhea and would not result in proliferative endometrium.

**Clinical Pearl / High-Yield Fact**
PCOS is a common endocrine disorder affecting women of reproductive age, characterized by chronic anovulation, insulin resistance, and hyperandrogenism. It is essential to recognize the clinical features of PCOS, including menstrual irregularities, hirsutism, and acne, and to perform a thorough physical examination and laboratory evaluation to confirm the diagnosis.

**Correct Answer:** D.

✓ Correct Answer: C. Dysfunctional uterine bleeding