Higher TSH Levels Within the Normal Range Are Associated With Unexplained Infertility

Area of Science:

• Reproductive Endocrinology
• Infertility Research
• Thyroid Function

Background:

• Unexplained infertility (UI) affects 10-30% of couples trying to conceive.
• While thyroid dysfunction and hyperprolactinemia are known infertility causes, the role of normal-range TSH and prolactin is unclear.
• Understanding UI mechanisms can lead to better, less invasive treatments.

Purpose of the Study:

• To compare thyrotropin (TSH) and prolactin levels in women with unexplained infertility (UI) versus controls.
• To investigate if normal-range TSH and prolactin levels are associated with UI.

Main Methods:

• A cross-sectional study compared 187 women with UI to 52 controls with normal fertility evaluations (except for severe male factor infertility).
• Participants had normal TSH (≤5 mIU/L) and prolactin (≤20 ng/mL) levels.
• TSH and prolactin levels were the primary outcome measures.

Main Results:

• Women with UI exhibited significantly higher TSH levels than controls (P = 0.003).
• This association remained significant after adjusting for age, BMI, and smoking.
• A higher proportion of women with UI (26.9%) had TSH ≥2.5 mIU/L compared to controls (13.5%; P < 0.05).
• No significant difference in prolactin levels was observed between groups.

Conclusions:

• Women experiencing unexplained infertility (UI) tend to have higher thyroid-stimulating hormone (TSH) levels compared to a control group.
• Further research is warranted to determine if treating elevated TSH levels within the normal range can enhance conception rates in couples with UI.