Thyroid status and renal function in older persons in the general population

Area of Science:

• Gerontology
• Endocrinology
• Nephrology

Background:

• Thyroid dysfunction and chronic kidney disease prevalence increase with age.
• Investigating the relationship between thyroid function and renal function in the elderly is crucial.

Purpose of the Study:

• To examine the cross-sectional association between thyroid function and renal function in 85-year-olds.
• To determine if low thyroid function at age 85 predicts accelerated renal function decline over 5 years.

Main Methods:

• 558 participants from the Leiden 85-plus Study were analyzed.
• Thyroid function (TSH, fT4, fT3) and renal function (eGFR) were measured at baseline (age 85) and annually for 5 years.
• Participants were categorized into thyroid function groups based on clinical cutoff values.

Main Results:

• Lower thyroid function (higher TSH, lower fT4/fT3) correlated with reduced renal function at baseline.
• Hypothyroidism and subclinical hypothyroidism were associated with lower eGFR compared to normal thyroid function (P=.004).
• No significant association was found between baseline thyroid function and the rate of change in renal function over follow-up.

Conclusions:

• Low thyroid function is associated with poorer renal function in very elderly individuals at a single point in time.
• Thyroid status at age 85 does not appear to influence the longitudinal decline in kidney function.
• The findings suggest thyroid function may not be causally linked to renal function deterioration in the oldest old.