ODP429 Treatment of high-normal TSH levels in women with unexplained infertility is associated with an increased conception rate

Unexplained infertility (UI), defined as the inability to conceive after 12 months of unprotected intercourse with no identified cause, affects up to 30% of infertile couples. Women with UI are significantly more likely to have a TSH level in the high-normal range (TSH between 2.5-5 mIU/L) as compared to a control population of women with infertility secondary to a partner with severe oligospermia. It is not known whether treating high-normal TSH levels with levothyroxine results in a higher rate of conception. We performed a cross-sectional study at a large academic health system in women with infertility and TSH levels between 2.5-5 mIU/L to compare rates of conception in women who were treated with levothyroxine versus those who were not treated with levothyroxine. We hypothesized that treatment with levothyroxine would result in a higher conception rate. We identified 126 women who presented for evaluation of infertility between 1/1/2000-6/30/2017 who met our inclusion criteria of a TSH in the high-normal range (2.5 mIU/L < TSH < 5 mIU/L) and either UI (80%, n=101) or infertility due to a severely oligospermic (semen concentration <1 million/mL) partner (20%, n=25). All subjects (n=126) had a normal prolactin level (< 20 ng/mL), regular menstrual cycles every 21-35 days with <5 days of inter-cycle variability, a day 3 follicle stimulating hormone (FSH)< 10 and no other identified cause of infertility. Male partners of women with unexplained infertility had a semen concentration of >15 million/mL, motility >40% and morphology >4% based on 2010 WHO criteria. Thirty-one percent (n=39) were treated with levothyroxine (LT+) by their primary providers, whereas 69% (n=87) were not treated with levothyroxine (LT-). Women treated with levothyroxine were older than those not treated (mean + SD, LT+: 32.5 + 2.4 years vs LT-: 31. 0 + 3. 0 years, p=0. 005) but were of similar BMI (median (interquartile range), LT+: 24.1 [21.7, 28.3] kg/m2 vs LT-: 23.6 [20.9, 27. 0] kg/m2, p=0.38). Baseline TSH was significantly higher in the group treated with levothyroxine (3.55 [3. 07, 4.19] mIU/L compared to the untreated group (2.93 [2.66, 3.40] mIU/L, p< 0. 0001). In women for whom follow-up data was available (n=105), a significantly higher percentage of women treated with levothyroxine (100%) achieved pregnancy compared to those not treated with levothyroxine (92%, p value 0. 027) and this was also true when only evaluating women with UI (n=86) (LT+: 100% versus LT-: 89.5%, p=0. 02). There was no significant difference in time to conception between the two groups (p=0.85). Women with high normal TSH levels (TSH between 2.5-5 mIU/L) treated with levothyroxine had a higher rate of conception compared to those not treated. Prospective, randomized studies are needed to determine whether treatment with levothyroxine could improve conception rates in patients with high-normal TSH levels. Presentation: No date and time listed