Age-related variation in thyroid function - a narrative review highlighting important implications for research and...

Area of Science:

• Endocrinology
• Gerontology
• Public Health

Background:

• Thyroid hormones are crucial for overall health and well-being.
• Standard laboratory reference intervals for thyroid function are widely used but may not be age-appropriate.
• Thyroid hormone levels naturally vary with age, necessitating a review of current practices.

Purpose of the Study:

• To review recent literature on age-related variations in thyroid function.
• To discuss the implications of these variations for clinical practice and research.
• To highlight the need for age-specific thyroid function reference intervals.

Main Methods:

• Literature review summarizing studies on age-related thyroid function.
• Analysis of age-specific trends in thyroid-stimulating hormone (TSH) and free triiodothyronine (FT3).
• Examination of differential health outcomes associated with thyroid hormone variations across age groups.

Main Results:

• Thyroid-stimulating hormone (TSH) levels are higher at the extremes of life, showing a U-shaped trend.
• Free triiodothyronine (FT3) levels decrease with age and correlate with fat mass during puberty.
• Thyroid function variations have differential health impacts: older adults may benefit from lower thyroid function, while younger individuals face risks from low-normal or high-normal levels.

Conclusions:

• Current thyroid hormone reference intervals may lead to undertreatment in older adults and missed interventions in younger populations.
• Age-appropriate reference intervals are essential for accurate diagnosis and management.
• Further research is required to validate age-specific ranges and understand thyroid hormone impacts in younger individuals.