Thyroid function and IVF outcome for different indications of subfertility.

Area of Science:

• Reproductive Endocrinology
• Thyroid Physiology

Background:

• Thyroid hormones are crucial for cellular function and fertility.
• Elevated thyroid-stimulating hormone (TSH) levels are associated with reduced pregnancy rates.
• Optimal TSH thresholds for assisted reproductive treatment (ART) remain debated.

Purpose of the Study:

• To investigate the association between high-normal TSH levels (2.5-4.5 mIU/L) and pregnancy outcomes in women undergoing conventional in vitro fertilization (IVF).
• To compare live birth rates in women with high-normal TSH versus low-normal TSH levels.

Main Methods:

• Retrospective analysis of 949 women undergoing conventional IVF between 2008 and 2012.
• Patients were stratified by TSH quartiles (0.3-4.5 mIU/L).
• Demographic and baseline characteristics were compared using ANOVA and chi-square tests.

Main Results:

• Women in the high-normal TSH quartile were more likely to have primary subfertility, particularly unexplained subfertility.
• These women had 15% fewer live births after IVF compared to those with lower TSH levels (P=0.02).
• In secondary subfertile women, high-normal TSH was associated with male factor subfertility and higher live birth rates (P=0.01).

Conclusions:

• High-normal TSH levels are associated with adverse pregnancy outcomes in primary unexplained subfertility cases undergoing IVF.
• In secondary subfertility, high-normal TSH, often linked to male factors, may be associated with improved IVF outcomes.
• The impact of TSH levels on IVF outcomes is dependent on the type and cause of subfertility.