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Age-related changes in thyroid structure and function in Sprague-Dawley rats.
S Rao-Rupanagudi1, R Heywood, C Gopinath
1Huntingdon Research Centre, United Kingdom.
Veterinary Pathology
|July 1, 1992
Summary
Aging Sprague-Dawley rats show significant thyroid changes, including decreased ultimobranchial cysts and reduced serum T3 and T4 hormone levels. These findings highlight age-related declines in thyroid function in this rat model.
Area of Science:
- Endocrinology
- Toxicology
- Comparative Pathology
Background:
- Thyroid gland aging involves complex structural and functional alterations.
- Previous documentation of age-related thyroid changes in Sprague-Dawley rats is limited.
- Understanding these changes is crucial for interpreting toxicity studies.
Purpose of the Study:
- To document age-related structural and functional changes in Sprague-Dawley rat thyroid glands.
- To investigate the impact of aging on thyroid hormone levels (T3 and T4).
- To provide a comprehensive baseline for thyroid gland morphology and function in aging rats.
Main Methods:
- Histopathological examination of thyroid glands from 1000 male and female Sprague-Dawley rats.
- Analysis of thyroid glands at multiple time points (8, 17, 30, 56, 108 weeks).
- Measurement of absolute and relative thyroid weights, body weights, and serum T3 and T4 concentrations.
Main Results:
- Decreased ultimobranchial cysts and increased C-cell hyperplasia with age.
- Development of hyperdistended thyroid follicles with abnormal colloid and flattened epithelium starting at 56 weeks.
- Increased absolute thyroid and body weights, decreased follicular epithelium height, and increased follicular diameter with age.
- Follicular tumors observed in 8% of males and 6% of females at 108 weeks.
- Marked reduction in serum T3 and T4 concentrations by 108 weeks of age.
Conclusions:
- Aging in Sprague-Dawley rats is associated with significant, previously undocumented, structural changes in the thyroid gland.
- Thyroid function, indicated by serum T3 and T4 levels, declines markedly in older rats.
- These age-related changes are important considerations for toxicological assessments in Sprague-Dawley rats.
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