This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Napoli, R. Articles by Saccà, L. Search for Related Content PubMed PubMed Citation Articles by Napoli, R. Articles by Saccà, L. Related Collections Thyroid Cardiovascular Endocrinology

Acute Effects of Triiodothyronine on Endothelial Function in Human Subjects

Departments of Internal Medicine and Cardiovascular Sciences (R.N., V.G., V.A., E.Z., C.D., M.M., U.O., L.S.) and Clinical Pathology (D.T., V.M.), University Federico II, 80131 Naples, Italy

Address all correspondence and requests for reprints to: Dr. R. Napoli, Department of Internal Medicine, Via Pansini, 80131 Napoli, Italy. E-mail: napoli{at}unina.it.

Context: Thyroid hormone regulates several cardiovascular functions, and low T₃ levels are frequently associated with cardiovascular diseases. Whether T₃ exerts any acute and direct effect on endothelial function in humans is unknown.

Objective: Our objective was to clarify whether acute changes in serum T₃ concentration affect endothelial function.

Design, Setting, and Subjects: Ten healthy subjects (age, 24 ± 1 yr) participated in a double-blind, placebo-controlled trial at a university hospital.

Interventions: T₃ (or placebo) was infused for 7 h into the brachial artery to raise local T₃ to levels observed in moderate hyperthyroidism. Vascular reactivity was tested by intraarterial infusion of vasoactive agents.

Main Outcome Measures: We assessed changes in forearm blood flow (FBF) measured by plethysmography.

Results: FBF response to the endothelium-dependent vasodilator acetylcholine was enhanced by T₃ (P = 0.002 for the interaction between T₃ and acetylcholine). The slopes of the dose-response curves were 0.41 ± 0.06 and 0.23 ± 0.04 ml/dl·min/µg in the T₃ and placebo study, respectively (P = 0.03). T₃ infusion had no effect on the FBF response to sodium nitroprusside. T₃ potentiated the vasoconstrictor response to norepinephrine (P = 0.006 for the interaction). Also, the slopes of the dose-response curves were affected by T₃ (1.95 ± 0.77 and 3.83 ± 0.35 ml/dl·min/mg in the placebo and T₃ study, respectively; P < 0.05). The increase in basal FBF induced by T₃ was inhibited by NG-monomethyl-L-arginine.

Conclusions: T₃ exerts direct and acute effects on the resistance vessels by enhancing endothelial function and norepinephrine-induced vasoconstriction. The data may help clarify the vascular impact of the low T₃ syndrome and point to potential therapeutic strategies.

This article has been cited by other articles:

				L. Sacca Heart Failure as a Multiple Hormonal Deficiency Syndrome Circ Heart Fail, March 1, 2009; 2(2): 151 - 156. [Full Text] [PDF]

				W. E. Visser, E. C. H. Friesema, and T. J. Visser Transport of Thyroxine and 3,3',5-Triiodothyronine in Human Umbilical Vein Endothelial Cells Endocrinology, March 1, 2009; 150(3): 1552 - 1557. [Abstract] [Full Text] [PDF]

				M. Dorr, K. Empen, D. M Robinson, H. Wallaschofski, S. B Felix, and H. Volzke The association of thyroid function with carotid artery plaque burden and strokes in a population-based sample from a previously iodine-deficient area Eur. J. Endocrinol., August 1, 2008; 159(2): 145 - 152. [Abstract] [Full Text] [PDF]

				R. Napoli, B. Biondi, V. Guardasole, C. D'Anna, A. De Sena, C. Pirozzi, D. Terracciano, C. Mazzarella, M. Matarazzo, and L. Sacca Enhancement of Vascular Endothelial Function by Recombinant Human Thyrotropin J. Clin. Endocrinol. Metab., May 1, 2008; 93(5): 1959 - 1963. [Abstract] [Full Text] [PDF]