Clinical Report: Investigation of Age and Sex Variability in Thyroid-Gonadal Axis Interactions

Overview

This study investigates the interactions between thyroid hormones and sex hormones in a cohort of 1,025 healthy individuals. It highlights significant age and gender differences in these associations, particularly among women of childbearing age.

Background

Understanding the interplay between the hypothalamic-pituitary-thyroid (HPT) axis and the hypothalamic-pituitary-gonadal (HPG) axis is crucial for comprehending reproductive health. Previous research has largely focused on individuals with thyroid dysfunction, leaving a gap in knowledge regarding those with normal thyroid function. This study aims to fill that gap by examining the associations in a healthy population.

Data Highlights

Key Findings

• FT4 was positively correlated with testosterone in men (Std β = 0.448, P = 0.002).
• No significant association was found in the overall female population, but trends varied by age.
• In females under 18, thyroid hormones and gonadotropins showed a negative correlation (FT3–LH: r = −0.372, P < 0.001).
• In the 18-40 age group, a positive correlation between FT4 and FSH was observed (r = 0.125, P = 0.001).
• Among women of childbearing age, FT4 was associated with FSH (Std β = 0.118, P = 0.005) and TSH with LH (Std β = 0.136, P < 0.001).

Clinical Implications

The findings suggest that normal fluctuations in thyroid hormone levels may influence reproductive endocrinology. Clinicians should consider age and gender when evaluating thyroid and reproductive hormone interactions in healthy individuals.

Conclusion

This study provides new insights into the complex interactions between thyroid and sex hormones in individuals with normal thyroid function, emphasizing the importance of considering age and gender in future research.

Related Resources & Content

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5. European Association of Urology Guidelines on Male Sexual and Reproductive Health: 2025 Update
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