Blum MR, et al. - In this randomized, double-blind, placebo-controlled trial, experts studied the effect of subclinical hypothyroidism (SHypo) treatment with levothyroxine on carotid atherosclerosis. In older persons with SHypo, normalization of thyroid-stimulating hormone (TSH) with levothyroxine was correlated with no difference in carotid intima media thickness (CIMT) and carotid atherosclerosis.

Methods

• This trial nested within the Thyroid Hormone Replacement for Subclinical Hypothyroidism trial.
• Study participants aged ≥ 65 years with SHypo (TSH, 4.60 to 19.99 mIU/L; free thyroxine level within reference range).
• Intervention was levothyroxine dose-titrated to achieve TSH normalization or placebo, including mock titrations.
• Main outcomes were CIMT, maximum plaque thickness measured with ultrasound.

Results

• As per data, 185 participants (mean age 74.1 years, 47% women, 96 randomized to levothyroxine) underwent carotid ultrasound.
• It was observed that mean TSH ± SD was 6.35 ± 1.95 mIU/L at baseline and decreased to 3.55 ± 2.14 mIU/L with levothyroxine vs 5.29 ± 2.21 mIU/L with placebo (P< 0.001).
• Researchers found that mean CIMT was 0.85 ± 0.14 mm under levothyroxine and 0.82 ± 0.13 mm under placebo (between-group difference = 0.02 mm; 95% CI, -0.01 to 0.06; P=0.30) after a median treatment of 18.4 months (interquartile range 12.2 to 30.0 months).
• Findings revealed that the proportion of carotid plaque was similar (n = 135; 70.8% under levothyroxine and 75.3% under placebo; P=0.46).
• It was noted that maximum carotid plaque thickness was 2.38 ± 0.92 mm under levothyroxine and 2.37 ± 0.91 mm under placebo (between-group difference -0.03; 95% CI, -0.34 to 0.29; P=0.86).
• No significant interactions were found between levothyroxine treatment and mean CIMT, according to sex, baseline TSH (categories 4.6 to 6.9, 7.0 to 9.9, and ≥10 mIU/L), or established cardiovascular disease (all P for interaction ≥ 0.14).