Growth hormone response to long-term GH-RH administration in lambs

Area of Science:

• Endocrinology
• Animal Science

Background:

• Growth hormone-releasing hormone (GHRH) regulates growth hormone (GH) secretion.
• Understanding long-term GHRH administration effects is crucial for therapeutic applications.
• Pituitary desensitization is a concern with continuous GHRH administration.

Purpose of the Study:

• To investigate the pattern of long-term GHRH administration for stimulating GH release.
• To determine if GHRH administration depletes pituitary GH content.
• To compare the effects of pulsatile versus continuous GHRH administration.

Main Methods:

• Two experiments using recently weaned male lambs.
• Groups received varied GHRH administration (continuous infusion, pulsatile injections) with or without somatostatin (SS) / octreotide.
• Plasma GH levels and pituitary GH content were measured.
• Response to intravenous GHRH challenge was assessed.

Main Results:

• Chronic pulsatile GHRH increased basal plasma GH levels, maintained over 3 weeks.
• Continuous GHRH administration did not increase basal GH levels.
• Pituitary GH content remained similar to controls in pulsatile GHRH groups.
• Pulsatile GHRH-treated animals showed a delayed GH response to GHRH challenge, recovering by week 3.

Conclusions:

• Long-term pulsatile GHRH administration stimulates GH release in growing male lambs.
• Pulsatile GHRH administration does not lead to pituitary desensitization.
• This administration pattern offers a potential strategy for managing GH-related conditions.