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


METHODS
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).


METHODS
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.
Napoli
Raffaele
R
Department of Internal Medicine and Cardiovascular Sciences, University Federico II, Naples, Italy. napoli@unina.it
Guardasole
Vincenzo
V
Zarra
Emanuela
E
D'Anna
Carolina
C
De Sena
Antonietta
A
Lupoli
Gelsy Arianna
GA
Oliviero
Ugo
U
Matarazzo
Margherita
M
Lupoli
Giovanni
G
Saccà
Luigi
L
D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology; D000208:Acute Disease; D000328:Adult; D001916:Brachial Artery / Q000187:drug effects / Q000502:physiology*; D002908:Chronic Disease; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D007037:Hypothyroidism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009599:Nitroprusside / Q000008:administration & dosage / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D009599:Nitroprusside; D000109:Acetylcholine