March 2002 -- Swiss researchers conducted a double blind study that was the first to show that use of levothyroxine in patients with subclinical hypothyroidism could help with cholesterol levels.

In the study, those patients who received levothyroxine therapy had total cholesterol reduction of 3.8%, and low density lipoprotein cholesterol reduction of 8.2% Patients also showed significant improvement in two clinical scores that assess the signs and symptoms of hypothyroidism.

Overall, the researchers estimated that treating subclinical hypothyroidism could reduce cardiovascular mortality risk from 9 to 31%.

(Source: "TSH-controlled L-thyroxine therapy reduces cholesterol levels and clinical symptoms in subclinical hypothyroidism: a double blind, placebo-controlled trial (Basel Thyroid Study)," Journal of Clinical Endocrinology and Metabolism, 2001 Oct;86(10):4860-6)