Related Experiment Videos
Influence of hyperthyroidism on growth hormone secretion
12a Divisione di Medicina Interna, Arcispedale S. Maria Nuova, Reggio Emilia, Italy.
Clinical Endocrinology
|May 1, 1993
Summary
Hyperthyroidism impairs growth hormone (GH) secretion due to reduced pituitary responsiveness and altered hypothalamic feedback. Treatment normalizes GH response to GHRH, indicating reversibility of these neuroendocrine changes.
Area of Science:
- Endocrinology
- Neuroendocrinology
- Metabolic Disorders
Background:
- Hyperthyroidism is known to affect growth hormone (GH) secretion.
- The precise mechanisms, whether pituitary somatotroph responsiveness or hypothalamic negative feedback, remain unclear.
Purpose of the Study:
- To investigate the neuroregulation of GH secretion in hyperthyroidism.
- To differentiate between pituitary and hypothalamic contributions to altered GH secretion.
Main Methods:
- Administered growth hormone-releasing hormone (GHRH) to hyperthyroid patients and controls.
- Assessed GH response after exogenous GH administration, oral glucose load, and TRH infusion.
- Repeated GHRH tests after methimazole-induced remission in hyperthyroid patients.
Main Results:
- Hyperthyroid patients exhibited blunted GH responses to GHRH, which improved after treatment.
- Serum IGF-I levels were elevated in hyperthyroidism and decreased post-treatment.
- Oral glucose suppressed GHRH-stimulated GH release in normal subjects but not in hyperthyroid patients.
Conclusions:
- Hyperthyroidism alters GH neuroregulation, decreasing pituitary responsiveness to GHRH and affecting hypothalamic glucose feedback.
- Exogenous GH and oral glucose appear to exert feedback through distinct mechanisms.
- Thyrotropin-releasing hormone (TRH) does not seem to play an inhibitory role in GH secretion in this context.