Carotid Intima-Media Thickness in Patients with Subclinical Hypothyroidism: A Prospective Controlled Study.

Purpose: The association between subclinical hypothyroidism (SCH) and cardiovascular risk, particularly with a TSH <10 µIU/ml, remains controversial. The objective of our study was to assess the association between SCH and cardiovascular risk through carotid intima-media thickness, and alternatively, to evaluate its change after treatment with levothyroxine.

Methods: A total of 54 individuals were included in the study: 18 with SCH; 18 with overt hypothyroidism (OH); and 18 healthy controls (HC). The carotid intima-media thickness was measured in each group. In SCH, follow-up was performed at three and six months after the start of levothyroxine treatment.

Results: The mean age of the total population at baseline was 35.8 years. The median TSH in SCH was 6.15 µIU/ml. The carotid intima-media thickness (mean and standard deviation) was greater in SCH in comparison to the HC group: right common carotid artery (RCCA), 0.486 ± 0.106 mm and 0.413 ± 0.075 mm in SCH and HC, respectively, p=0.01 and left common carotid artery (LCCA), 0.511 ± 0.144 mm and 0.427 mm ± 0.090 in SCH and HC, respectively, p=0.03). In patients with SCH, there was a decrease in the carotid intima-media thickness after treatment with levothyroxine (RCCA and LCCA, p <0.05 at three and six months).

Conclusions: There was an association between increased carotid intima-media thickness in patients with SCH in comparison with HC, even with a TSH <10 µIU/ml. The increase was reversed with levothyroxine therapy. The association of this increased thickness with important cardiovascular outcomes remains uncertain and should be evaluated in future studies.