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Levothyroxine decreases remnant-like lipoprotein cholesterol in subclinical hypothyroidism
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Higher levels of remnant-like lipoproteins were found among women with subclinical hypothyroidism compared with controls, and levothyroxine therapy significantly decreased these levels, according to study data.
Researchers said levothyroxine therapy also increased hepatic lipase activity, which may explain the decrease in remnant-like lipoprotein cholesterol levels.
Gabriela Brenta, MD, of the department of endocrinology at Cesar Milstein Hospital in Buenos Aires, Argentina, and colleagues evaluated 37 women with subclinical hypothyroidism and 29 women as controls to determine remnant-like lipoproteins and small, dense LDL levels and hepatic lipase activity in subclinical hypothyroidism. A subgroup of 22 women with subclinical hypothyroidism was evaluated for effects of levothyroxine therapy.
Compared with controls, the subclinical hypothyroidism group had higher remnant-like lipoprotein cholesterol levels (P = .005) and remnant-like lipoprotein triglyceride levels (P = .033). However, no differences were found between the groups for small, dense LDL and hepatic lipase activity.
HDL levels decreased after levothyroxine therapy (P = .04). After 6 months of levothyroxine therapy, hepatic lipase activity increased (P = .012) and was negatively correlated with remnant-like lipoprotein cholesterol levels (P = .006) and remnant-like lipoprotein triglyceride levels (P = .03).
“Women with [subclinical hypothyroidism] have increased levels of [remnant-like lipoproteins] when compared with euthyroid women, and [remnant-like lipoprotein cholesterol levels], in particular, decrease following treatment with levothyroxine,” the researchers wrote. “Furthermore, [hepatic lipase] activity also increases after levothyroxine treatment, and this could be interpreted as one possible explanation for the decrease of [remnant-like lipoprotein cholesterol], in addition to hepatic overproduction of triglyceride-rich precursor particles and a decrease in the specific receptors. These findings highlight the atherogenic impact of impaired lipoprotein metabolism despite normal plasma lipid levels in [subclinical hypothyroidism] and contribute to improving our understanding of the pathophysiological mechanisms of lipid metabolism associated with mild hypothyroidism, while confirming the effectiveness of levothyroxine treatment.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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