Orouji Jokar, T., Fourman, L. T., Lee, H., Mentzinger, K., & Fazeli, P. K. (2018). Higher TSH Levels Within the Normal Range Are Associated With Unexplained Infertility. The Journal of Clinical Endocrinology and Metabolism, 103(2), 632-639. https://doi.org/10.1210/jc.2017-02120
Orouji Jokar T, Fourman LT, Lee H, Mentzinger K, Fazeli PK. Higher TSH Levels Within the Normal Range Are Associated With Unexplained Infertility. J Clin Endocrinol Metab. 2018;103(2):632-639. doi:10.1210/jc.2017-02120
Orouji Jokar, Tahereh, et al. "Higher TSH Levels Within the Normal Range Are Associated With Unexplained Infertility." The Journal of Clinical Endocrinology and Metabolism, vol. 103, no. 2, 2018, pp. 632-639.
Women with unexplained infertility had higher normal-range TSH
Women with unexplained infertility had higher TSH levels, still within the normal range. A cross-sectional study at one academic health system compared 239 women. About 27 out of 100 women with unexplained infertility had a TSH in the upper part of normal. In the comparison group, about 14 out of 100 did.
Key Findings
The study included 187 women with unexplained infertility and 52 women whose partners had azoospermia (no sperm in the semen) or severe oligospermia (very low sperm count), seen from 2000 to 2012.
Median TSH was significantly higher in the unexplained infertility group than in the comparison group (P = 0.003). The difference remained significant after controlling for age, body mass index, and smoking status.
26.9% of women with unexplained infertility had a TSH in the upper part of the normal range, compared with 13.5% of the comparison group (P < 0.05).
Prolactin levels were similar in the two groups (P = 0.36).
Only 19 of the 239 women had thyroid peroxidase antibodies measured around the time of their infertility evaluation.
Interpretation
This cross-sectional study compared women evaluated for infertility. Women with unexplained infertility had a higher median TSH than the comparison group. The gap held even after accounting for age, weight, and smoking status. Every woman's TSH and prolactin fell within the normal range, and none had known thyroid disease. The findings support larger studies testing whether treating high-normal TSH shortens time to conception.
RRM Context
Unexplained infertility means the cause is still undiagnosed. This study points to one possible hormonal piece inside the normal range. Guidelines the authors cite call for checking TSH in every woman seeking an infertility evaluation. Restorative reproductive medicine keeps searching for causes like this. IVF bypasses the question of why conception has not happened.
Our editorial summary of this paper, not the article's abstract.
Abstract
Context
Unexplained infertility (UI), defined as the inability to conceive after 12 months of unprotected intercourse with no diagnosed cause, affects 10% to 30% of infertile couples. An improved understanding of the mechanisms underlying UI could lead to less invasive and less costly treatment strategies. Abnormalities in thyroid function and hyperprolactinemia are well-known causes of infertility, but whether thyrotropin (TSH) and prolactin levels within the normal range are associated with UI is unknown.
Objective
To compare TSH and prolactin levels in women with UI and women with a normal fertility evaluation except for an azoospermic or severely oligospermic male partner.
Design, Setting, and Participants
Cross-sectional study including women evaluated at a large academic health system between 1 January 2000 and 31 December 2012 with normal TSH (levels within the normal range of the assay and ≤5 mIU/L) and normal prolactin levels (≤20 ng/mL) and either UI (n = 187) or no other cause of infertility other than an azoospermic or severely oligospermic partner (n = 52).
Main Outcome Measures
TSH and prolactin.
Results
Women with UI had significantly higher TSH levels than controls [UI: TSH 1.95 mIU/L, interquartile range: (1.54, 2.61); severe male factor: TSH 1.66 mIU/L, interquartile range: (1.25, 2.17); P = 0.003]. This finding remained significant after we controlled for age, body mass index, and smoking status. Nearly twice as many women with UI (26.9%) had a TSH ≥2.5 mIU/L compared with controls (13.5%; P < 0.05). Prolactin levels did not differ between the groups.
Conclusions
Women with UI have higher TSH levels compared with a control population. More studies are necessary to determine whether treatment of high-normal TSH levels decreases time to conception in couples with UI.
002pd6e78 