Thyrotropin-releasing hormone increases plasma norepinephrine in man

Area of Science:

• Endocrinology
• Cardiovascular Physiology

Background:

• Thyrotropin-releasing hormone (TRH) is a key regulator of thyroid-stimulating hormone.
• The cardiovascular and hormonal effects of exogenous TRH in humans are not fully elucidated.

Purpose of the Study:

• To investigate the effects of exogenous TRH administration on blood pressure and key hormonal systems in humans.
• To determine the role of catecholamines, renin-angiotensin-aldosterone system, and prolactin in TRH-mediated physiological responses.

Main Methods:

• Administration of exogenous TRH to human subjects.
• Measurement of mean arterial blood pressure.
• Assay of plasma norepinephrine, epinephrine, renin activity, and aldosterone levels.

Main Results:

• TRH administration significantly increased mean arterial blood pressure at 4 and 8 minutes post-administration.
• Plasma norepinephrine levels increased significantly following TRH administration.
• No significant alterations were observed in plasma epinephrine, renin activity, or aldosterone levels.

Conclusions:

• TRH administration induces an increase in circulating catecholamines, primarily norepinephrine, in humans.
• The observed increases in blood pressure following TRH administration are likely mediated by norepinephrine release.
• Acute elevations in prolactin do not appear to influence the renin-angiotensin-aldosterone system in humans.