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Pulsatile thyrotropin secretion in patients with Addison's disease during variable glucocorticoid therapy
J Hangaard1, M Andersen, E Grodum
1Department of Endocrinology, Odense University Hospital, Denmark.
The Journal of Clinical Endocrinology and Metabolism
|July 1, 1996
Summary
Physiological cortisol levels influence thyroid-stimulating hormone (TSH) secretion. Even normal cortisol levels inhibit TSH, with higher doses causing greater suppression, impacting pituitary sensitivity to TRH.
Area of Science:
- Endocrinology
- Hormone Regulation
- Pituitary-Thyroid Axis
Background:
- The relationship between serum cortisol levels and TSH secretion is complex.
- Addison's disease provides a model to study cortisol's effects due to dysregulated levels.
Purpose of the Study:
- To investigate the inhibitory effects of physiological and pathophysiological serum cortisol on TSH secretion.
- To determine the dose-dependent action of glucocorticoids on TSH release and TRH response.
Main Methods:
- 12 patients with Addison's disease underwent three infusion protocols: conventional hydrocortisone (HC) substitution, placebo after HC withdrawal, and high-dose HC after dexamethasone priming.
- Serum cortisol and TSH levels were monitored, including pulsatility, with TRH stimulation tests.
- HC infusions mimicked normal diurnal cortisol rhythms.
Main Results:
- Medium HC doses normalized serum cortisol and TSH pulsatility, similar to controls (TSH: 1.0 +/- 0.5 mU/L).
- Low cortisol states (placebo) significantly increased TSH levels (2.0 +/- 1.6 mU/L, P < 0.05).
- High HC doses significantly suppressed TSH (0.4 +/- 0.2 mU/L, P < 0.05) and reduced pulse frequency (P < 0.01).
Conclusions:
- Glucocorticoids exert a dose-dependent inhibition on TSH secretion.
- Physiological serum cortisol levels influence endogenous TSH secretion.
- Cortisol likely regulates pituitary sensitivity to thyrotropin-releasing hormone (TRH).