Impaired endothelial- and nonendothelial-mediated vasodilation in patients with acute or chronic hypothyroidism

• Published in: Clinical endocrinology (Oxford) Vol. 72; no. 1; pp. 107 - 111
• Main Authors: Napoli, Raffaele, Guardasole, Vincenzo, Zarra, Emanuela, D'Anna, Carolina, De Sena, Antonietta, Lupoli, Gelsy Arianna, Oliviero, Ugo, Matarazzo, Margherita, Lupoli, Giovanni, Saccà, Luigi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-01-2010; Blackwell; Wiley Subscription Services, Inc
• Subjects: Acetylcholine - administration & dosage; Acetylcholine - pharmacology; Acute Disease; Adult; Biological and medical sciences; Brachial Artery - drug effects; Brachial Artery - physiology; Chronic Disease; Dose-Response Relationship, Drug; Endocrinopathies; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; Female; Forearm - blood supply; Fundamental and applied biological sciences. Psychology; Humans; Hypothyroidism - physiopathology; Male; Medical sciences; Middle Aged; Nitroprusside - administration & dosage; Nitroprusside - pharmacology; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Regional Blood Flow - drug effects; Thyroid. Thyroid axis (diseases); Vasodilation - drug effects; Vasodilation - physiology; Vertebrates: endocrinology; Endocrinopathy; Human; Vasomotricity; Endothelial cell; Chronic; Acute; Thyroid diseases; Patient; Hypothyroidism; Endocrinology; Vasodilation; Endothelium
• ISSN: 0300-0664; 1365-2265
• DOI: 10.1111/j.1365-2265.2009.03609.x

Summary
Objective  Vascular dysfunction and accelerated atherosclerosis are prominent features of hypothyroidism. The relative roles of thyroid hormone (TH) deficiency and the associated vascular risk conditions are still unclear. We studied the impact of acute and chronic hypothyroidism on vascular reactivity.
Patients  We studied 12 patients with chronic primary hypothyroidism (cHY; TSH: 52 ± 14 mU/l), seven patients with acute hypothyroidism secondary to total thyroidectomy (aHY; TSH: 97 ± 24) and 13 healthy subjects (TSH: 1·2 ± 0·5).
Measurements  We measured forearm blood flow (FBF) using plethysmography during intra‐brachial infusion of: acetylcholine (ACh), sodium nitroprusside (NP) and norepinephrine (NE). We also measured serum C‐reactive protein (CRP), TNF‐alpha, asymmetric dimethylarginine (ADMA) and the forearm balance of nitric oxide (NO) during ACh infusion.
Results  As compared with the controls, the vasodilatory response to ACh was reduced in cHY (P = 0·001) and aHY (P = 0·04), as was the forearm release of NO (P < 0·05). During NP infusion, FBF rose to 24 ± 2 ml/dl/min in the controls and to significantly lower values in cHY (12 ± 1; P = 0·001) and aHY (15 ± 2; P = 0·004). NE‐induced vasoconstriction was similar in the controls and aHY, but blunted in cHY. Serum CRP, TNF‐alpha and ADMA were not different in the three groups.
Conclusions  (i) Hypothyroidism associates with endothelial and nonendothelial mediated vascular dysfunction; (ii) these defects are evident even after short‐term hypothyroidism, indicating that TH deficiency per se is sufficient to alter vascular homeostasis; and (iii) chronic, but not acute, hypothyroidism impairs the vasoconstrictory effect of NE in the resistance vessels.