Background: The association between subclinical hypothyroidism (SCH) and cardiovascular risk, particularly with a TSH <10µIU/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. 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 was greater in SCH in comparison to the HC group (Right common carotid artery [RCCA, mm]: 0.486 ± 0.106 and 0.413 ± 0.075 in SCH and HC, respectively, p=0.01. Left common carotid artery [LCCA, mm]: 0.511±0.144 and 0.427±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 3 and 6 months). Conclusions: There is an association between an increase in the carotid intima-media thickness in patients with SCH in comparison to HC, even with a TSH <10 µIU/ml. The increase reversed with levothyroxine therapy. Its association with important cardiovascular outcomes remains uncertain and should be evaluated in future studies.