What is the diagnosis and recommended management for a 19‑year‑old obese female with oligomenorrhea (five menses in the past year), acne, low sex‑hormone‑binding globulin, and normal total testosterone, thyroid‑stimulating hormone, prolactin, and 17‑hydroxyprogesterone levels?

Diagnosis: Polycystic Ovary Syndrome (PCOS)

This 19-year-old patient meets diagnostic criteria for PCOS based on the Rotterdam criteria—she has both ovulatory dysfunction (oligomenorrhea with only 5 menses per year) and clinical hyperandrogenism (acne, obesity, low SHBG)—even though her total testosterone is normal. 1

Why PCOS Despite Normal Testosterone

• Total testosterone is abnormal in only 70% of women with confirmed PCOS, meaning 30% have normal testosterone levels despite having the condition. 1
• Low sex hormone-binding globulin (SHBG) of 15.8 is characteristic of PCOS and indicates elevated free (bioavailable) testosterone even when total testosterone appears normal. 1, 2
• The Rotterdam criteria require only two of three features (oligo/anovulation, clinical/biochemical hyperandrogenism, polycystic ovarian morphology) after exclusion of other conditions—this patient has ovulatory dysfunction plus clinical hyperandrogenism (acne, obesity, low SHBG). 1, 3
• Clinical hyperandrogenism alone (acne, hirsutism, or alopecia) plus irregular cycles is sufficient for diagnosis without requiring abnormal laboratory values. 1

Complete the Diagnostic Workup

Additional Laboratory Tests Needed

• Measure calculated free testosterone or Free Androgen Index (FAI) using the formula FAI = (total testosterone/SHBG) × 100, which will likely be elevated given her low SHBG and is more sensitive (89% sensitivity) than total testosterone alone. 1, 4
• Obtain a 2-hour oral glucose tolerance test with 75g glucose load to screen for impaired glucose tolerance or type 2 diabetes, as PCOS patients are four times more likely to develop diabetes. 1, 5, 3
• Perform a fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) because metabolic syndrome is twice as common in PCOS patients. 1, 5, 3

Imaging

• Transvaginal ultrasound is not mandatory for diagnosis since she already meets two Rotterdam criteria (ovulatory dysfunction + clinical hyperandrogenism), but it would identify the complete PCOS phenotype if ≥20 follicles per ovary or ovarian volume >10 mL are present. 1, 5

Management Strategy

First-Line: Lifestyle Modification

• Weight loss of 5–10% of initial body weight is first-line therapy and significantly improves ovulation rates, metabolic parameters, and androgen levels in overweight/obese PCOS patients. 1, 5, 3
• All individuals with PCOS should receive multicomponent lifestyle intervention (dietary modification, structured physical activity, behavioral counseling) regardless of BMI, because insulin resistance is present independent of body weight. 5

Pharmacologic Management (Since Fertility Not Desired)

• Combined oral contraceptive pills (OCPs) are first-line therapy to suppress ovarian androgen production, raise SHBG (which will lower free testosterone), improve acne, regulate menstrual cycles, and provide endometrial protection against unopposed estrogen. 1, 5, 3
• Metformin should be added to improve insulin sensitivity, decrease circulating androgens, promote modest weight loss, and reduce metabolic risk (hyperglycemia, dyslipidemia). 1, 5, 3

Long-Term Monitoring

• Monitor weight, blood pressure, fasting lipid panel, and glucose control every 6–12 months because PCOS confers lifelong increased risk of type 2 diabetes, dyslipidemia, and cardiovascular disease. 1, 5
• Screen for anxiety, depression, body-image concerns, and eating disorders at baseline and periodically, as these conditions are highly prevalent in PCOS. 5
• Measure serum 25-hydroxy-vitamin D to identify deficiency, which is present in 67–85% of PCOS patients. 5

Critical Pitfalls to Avoid

• Do not dismiss PCOS based on normal total testosterone alone—low SHBG indicates elevated free testosterone, and 30% of PCOS patients have normal total testosterone. 1
• Do not use LH/FSH ratio as a diagnostic criterion—it is abnormal in only 35–44% of PCOS women and is a poor standalone marker. 1
• Do not delay metabolic screening—all PCOS patients require glucose tolerance testing and lipid panels regardless of age or BMI. 1, 5
• Recognize that OCPs reduce endometrial cancer risk associated with chronic unopposed estrogen exposure from anovulation. 1
• Address weight stigma and provide culturally sensitive counseling to improve adherence to lifestyle interventions. 5