Changes in somatotropin and thyrotropin secretory patterns in aging rats

Area of Science:

• Endocrinology
• Neuroendocrinology
• Aging Research

Background:

• Aging is associated with significant physiological changes, including alterations in hormone secretion.
• The relationship between pituitary gland size and hormone secretion patterns in aging animals requires further clarification.

Purpose of the Study:

• To investigate the influence of pituitary enlargement on growth hormone (GH) and thyrotropin (TSH) secretory patterns in aging Sprague-Dawley rats.
• To examine the correlation between anterior pituitary (AP) weight and plasma GH and TSH levels across different age groups and sexes.

Main Methods:

• Used young, old, and senescent female rats and young and old male rats.
• Collected sequential blood samples from conscious, undisturbed animals via chronic intraatrial cannulas.
• Measured plasma GH, TSH, serum thyroxine (T4), and triiodothyronine (T3) using radioimmunoassay.

Main Results:

• GH pulse amplitude declined with age in both sexes by two years, but senescent females showed increased GH pulse amplitude, trough levels, and mean plasma GH compared to old females.
• A significant positive correlation was found between mean plasma GH and AP weight in females (p < 0.01), but not in males.
• Old and senescent rats exhibited lower serum T4 and higher plasma TSH levels compared to young rats, irrespective of sex.

Conclusions:

• Pituitary enlargement is linked to altered GH secretion in aging female rats.
• Aging significantly impacts GH and thyroid hormone regulation, with sex-specific differences observed in GH dynamics.
• TSH levels increase with age, while T4 levels decrease, suggesting age-related changes in thyroid function.