At the screening visit, blood pressure and heart rate will be measured, weight and height obtained and body mass index calculated (kg/m2). If not already completed at their new patient visit, transvaginal ultrasound will be performed to assess uterine anatomy and obtain antral follicle count, TSH, prolactin, and testosterone will be drawn, and serum samples will be obtained and analyzed for metabolic parameters (fasting lipids, insulin, and complete metabolic panel). One additional tube of blood will be drawn to store for potential future analysis. Once enrolled, randomization will occur and subjects will start either inositols or placebo. 84 women will be stratified by BMI and randomized 1:1 into two treatment arms, A) "Control Arm" = twice daily placebo powder and B) "Inositol Arm" = twice daily myo-inositol (2,000mg) plus d-chiro-inositol (50mg) supplement powder.

Treatment with either placebo or inositol will begin upon randomization. Participants will complete a validated quality of life in PCOS questionnaire (PCOSQ) at this visit and again upon study completion (11). Treatment with letrozole will begin after the baseline visit, which will occur after spontaneous menses or withdrawal bleeding induced by progestin administration. Because of this timing, participants will undergo pretreatment with inositol or placebo for a variable amount of time up to 6 weeks, with an anticipated average of 2-3 weeks. Metabolic parameters will be repeated after approximately 6 (7-9) and approximately 12 (11-13) weeks of inositol or placebo, at whichever study visit is most proximal in time to this goal timeframe. Both groups will receive letrozole 5mg every day for 5 days on days 3-7 of their menstrual cycle and instructed on timing intercourse with anticipated ovulation dates. Blood will be drawn for a serum progesterone each cycle between cycle days 20-22 to confirm ovulation, and repeated 1 week later if the initial progesterone level is below the threshold to confirm ovulation. Once ovulation is confirmed, they patient will expect a period 7-10 days later. They will call with cycle day 1 of bleeding if it occurs to start their next cycle of treatment, up to 5 cycles. If no bleeding occurs within the expected timeframe, they will check a home pregnancy test and call with results. Patients will complete medication side effect questionnaires at the first blood draw for progesterone of each cycle. This will be reviewed same-day and in person with the research nurse coordinator. Each patient will complete up to 5 cycles. Dose of letrozole will be increased in subsequent cycles for non-response or late ovulatory response (ovulation later than the progesterone blood draw) up to 10mg of letrozole a day. For patients with a second progesterone level below the threshold to confirm ovulation (day 21 and day 28), the higher dose of letrozole will be initiated following the receipt of the second low progesterone result. For patients who do not ovulate on the maximum dose of letrozole, their study participation will be considered complete.

Data to be collected will include: demographic information and medical history \[age, race/ethnicity, body mass index (BMI), antral follicle count, length of infertility, prior infertility treatment (yes or no), obstetrical history, medical history, surgical history, current medication and allergy lists\], partner information \[age, race/ethnicity, BMI, general medical health assessment, prior paternity history\], transvaginal ultrasound results, and serum studies \[TSH, prolactin, progesterone, hCG levels, androgen levels (total and free testosterone, SHBG), and metabolic factors (fasting lipid panel, fasting glucose, fasting insulin, glucose:insulin ratio, HOMA-IR index)\]. Questionnaires to be completed include: PCOSQ validated questionnaire for PCOS-related quality of life, and a side effect questionnaire about known side effects of letrozole and inositols. In addition to the baseline transvaginal ultrasound, additional ultrasounds may be performed as indicated clinically (including for establishing clinical pregnancy). Pertinent demographic and clinical information on patients who are participating in the study will be entered into a study database REDCap secure software.

Using the reported clinical pregnancy rate for infertile PCOS patients treated with letrozole of 31.3% (12) as the control group proportion (0.31) with a goal of 10% effect size (and therefore treatment group proportion 0.41), an alpha of 0.05, and power of 0.8, our sample size is estimated (for a full clinical trial) at \~361 in each arm. In considering the previously observed drop-out rate of \~20% in a similar patient population (3), we estimate that for a full clinical trial, we would need 452 participants randomized in each arm. Based on previously published literature regarding estimation of pilot randomized trial sample sizes, we will target 9% of this sample size for our pilot study to suggest or identify a significant difference (13). In conclusion, our planned study size will be 42 participants in each study arm.