BackgroundTo assess whether elevated thyroid-stimulating hormone (TSH) levels before conception can predict poor outcomes of assisted reproductive technology (ART).MethodsPrior to July 2018, we searched the PubMed, EMBASE, COCHRANE, Google Scholar, and CNKI databases for studies. Retrospective or prospective reports that compared ART results in patients with subclinical hypothyroidism (SCH) with normal thyroid function were selected. Two reviewers separately reviewed each potential article for qualification, analyzed the quality of the studies according to the Newcastle-Ottawa scale, and extracted the data. The PRISMA guidelines were adopted.ResultsWe selected a total of 18 publications that included 14,846 participants for this meta-analysis. When the TSH cut-off value for SCH was set at 2.5 mIU/L, no significant differences were observed in ART-related outcomes between SCH patients and normal women. The evaluated outcomes included the live birth rate (LBR) (OR: 0.93; 95% CI (0.77,1.12), P = 0.43), clinical pregnancy rate (CPR) (OR:1.02; 95% CI (0.90,1.17); P = 0.74), pregnancy rate (PR) (OR: 1.00; 95% CI (0.89,1.12); P = 0.99), and miscarriage rate (MR) (OR:1.24; 95% CI (0.85, 1.80); P = 0.26). Furthermore, when a higher TSH level was used as the cut-off value to diagnose SCH (i.e., 3.5–5 mIU/L), a significant difference was found in the MR (OR: 1.91; 95% CI (1.09, 3.35); P = 0.02) between the two groups of ART-treated women. However, when a broader cut-off value was used to define SCH, no significant differences were observed in the LBR (OR: 0.72; 95% CI (0.47,1.11); P = 0.14), CPR (OR: 0.82; 95% CI (0.66,1.00); P = 0.052), or PR (OR: 1.07; 95% CI (0.72,1.60); P = 0.74) between the two groups of ART-treated women.ConclusionNo difference was observed in ART outcomes when a TSH cut-off value of 2.5 mIU/L was used. However, when a broader TSH cut-off value was used, preconception SCH resulted in a higher miscarriage rate than in normal women.Electronic supplementary materialThe online version of this article (10.1186/s12958-018-0424-0) contains supplementary material, which is available to authorized users.

The objective of this study was to evaluate the relationship between subclinical hypothyroidism (SCH) and depression. We also analysed the effect of levothyroxine (L-T4) on depression in SCH patients. We found an insignificant difference for the composite endpoint: standard mean difference (SMD) of 0.23 (95% confidence interval (CI) −0.03, 0.48, P = 0.08, I2 = 73.6%). The odds ratio (OR) for depressive patients was 1.75 (95% CI 0.97, 3.17 P = 0.064, I2 = 64.6%). Furthermore, sub-group analysis according to age found that SCH was related to depression in younger patients (<60 years old), as defined by the diagnosis of depression: OR of 3.8 (95% CI 1.02, 14.18, P = 0.047, I2 = 0.0%) or an increase on the depressive scale: SMD of 0.42 (95% CI 0.03, 0.82, P = 0.036, I2 = 66.6%). Meanwhile, SCH did not associate with depression in older patients (≥60 years old), as defined by the diagnosis of depression: OR of 1.53 (95% CI 0.81, 2.90, P = 0.193, I2 = 71.3%) or an increase on the depressive scale: SMD of 0.03 (95%CI −0.31, 0.37, P = 0.857, I2 = 79.8%). We also found an insignificant difference in the composite endpoint between the L-T4 supplementation group and placebo group in SCH patients. The estimated SMD was 0.26 (95% CI −0.09, 0.62, P = 0.143, I2 = 52.9%). This meta-analysis demonstrates that SCH is not connected to depression. However, sub-group analysis according to age found that SCH is related to depression in younger patients, but not in older patients. Furthermore, we failed to find an effect of L-T4 supplementation treatment for SCH on depression.