Coronary flow reserve is impaired in subclinical hypothyroidism.
OBJECTIVE
Although the cardiovascular system is highly sensitive to thyroid hormones, the cardiovascular effects of subtle thyroid dysfunction such as subclinical hypothyroidism (SHT) remain unclear. Therefore, we investigated coronary flow reserve (CFR) reflecting coronary microvascular function in patients with SHT.


METHODS
Fifty subjects with SHT and 30 control subjects with normal serum thyroid hormones and TSH levels were included in this study. Coronary diastolic peak flow velocities were measured at baseline and after dipyridamole infusion. CFR was calculated as the ratio of hyperemic to baseline diastolic peak velocity.


RESULTS
Age, gender, diastolic and systolic blood pressure, body mass index (BMI), serum lipid parameters, and thyroid hormone levels were similar between the groups. Heart rate was significantly lower in the SHT group. Left ventricular diastolic filling parameters were significantly different in the SHT group while other echocardiographic parameters were similar. CFR values were significantly lower in subjects with SHT than in the control group (2.38 +/- 0.44 vs. 2.98 +/- 0.47, p < 0.0001).


CONCLUSIONS
These findings suggest that CFR, which reflects coronary microvascular function, is impaired in patients with SHT.
Baycan
Semra
S
Cardiology Department, Baskent University, Faculty of Medicine, Ankara, Turkey. semrab@baskent-kon.edu.tr
Erdogan
Dogan
D
Caliskan
Mustafa
M
Pamuk
Baris Onder
BO
Ciftci
Ozgur
O
Gullu
Hakan
H
Yildirir
Aylin
A
Guvener
Nilgun D
ND
Muderrisoglu
Haldun
H
D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D015992:Body Mass Index; D016022:Case-Control Studies; D003326:Coronary Circulation; D003971:Diastole; D004452:Echocardiography / Q000379:methods; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology; D013972:Thyrotropin / Q000378:metabolism
D013972:Thyrotropin