Carotid integrated backscatter analysis in patients with subclinical hypothyroidism

Abstract

Objective: The aim of the present study was to determine whether integrated backscatter (IBS) analysis combined with conventional ultrasonography could differentiate the tissue characteristics of carotid artery intimal hyperplasia in patients with subclinical hypothyroidism (SH).

Methods: Forty-one patients with SH, as judged by elevated serum TSH levels and free thyroid hormones within the normal range, and 31 sex- and age-matched euthyroid volunteers underwent two-dimensional conventional ultrasonography and IBS analysis of the carotid wall. Carotid intima-media thickness (IMT) and corrected IBS (C-IBS), an index of arterial wall degeneration and fibrosis, were evaluated.

Results: Mean IMT as well C-IBS values were higher in SH than in controls (P < 0.0001 for both), whereas the carotid diameter was not significantly different between the two groups. The distribution of C-IBS values in each group showed that regions with higher C-IBS values were found more frequently in SH patients than in control subjects. The percentage of regions that could be considered as fibromatous (C-IBS value from -18 to -21 dB) was 28% in SH and 9% in euthyroid subjects (P < 0.0001). In the SH group, C-IBS values were significantly and positively associated with plasma TSH (r = 0.32, P < 0.05 and r = 0.59, P < 0.0001, respectively) and with both total cholesterol (r = 0.46, P = 0.01) and low density lipoprotein (LDL)-cholesterol (r = 0.55, P = 0.001).

Conclusions: Carotid IMT in subclinically hypothyroid patients is higher than that in euthyroid controls. This is characterized by increased IBS values, which are related to the collagen content of the arterial wall. The severity of this remodelling process seems to be related to TSH and cholesterol levels.