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Increasing age impairs the thyroid hormone response to overfeeding
1Department of Medicine, North Shore University Hospital, Manhasset, New York 11030.
Summary
Calorie overfeeding increases triiodothyronine (T3) in young rats but not older rats, impacting thyroid hormone metabolism differently with age. Aging decreases T3 and thyroxine (T4) production and clearance rates.
Area of Science:
- Endocrinology
- Aging Research
- Nutritional Science
Background:
- Aging in humans and rodents is linked to increased body weight and fat mass.
- In young rats, overfeeding elevates triiodothyronine (T3) production and reduces weight gain efficiency.
Purpose of the Study:
- To investigate age-dependent responses in thyroxine (T4) and T3 metabolism during mixed calorie overfeeding.
- To compare the effects of overfeeding on thyroid hormone dynamics in 4-month-old versus 14-month-old rats.
Main Methods:
- Male Sprague-Dawley rats (4 and 14 months old) were fed either a control (CHOW) or a chow + mixed calorie (CAFE) diet for 28 days.
- Body weight, caloric intake, serum T4 and T3 concentrations, and metabolic clearance and production rates of T3 and T4 were measured.
- Liver type I iodothyronine 5'-deiodinase activity was assessed.
Main Results:
- Overfeeding increased body weight gain in both age groups, but more significantly in younger rats.
- Serum T3 increased in young overfed rats but remained unchanged in older overfed rats.
- T3 and T4 metabolic clearance and production rates decreased with age and were altered by overfeeding differently in young versus old rats.
Conclusions:
- Aging significantly alters thyroid hormone metabolism, reducing T3 and T4 production and clearance rates.
- Calorie overfeeding impacts T3 metabolism in young rats but not in older rats, suggesting an age-related decline in adaptive responses.
- Liver type I iodothyronine 5'-deiodinase activity, crucial for T3 production, increased with overfeeding in young rats but not in older rats.