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Changes in serum apolipoprotein concentrations after L-thyroxine therapy in infants with congenital hypothyroidism
T Asami1, T Ciomartan, M Uchiyama
1Department of Pediatrics, School of Medicine, Niigata University, Japan.
Insights
Thyroid hormone replacement therapy in infants with congenital hypothyroidism led to decreased high-density lipoprotein cholesterol (HDLC) and apolipoprotein A-I (apo A-I) levels. These changes suggest thyroid hormones influence lipid metabolism in infants.
Area of Science:
- Endocrinology
- Pediatric Lipid Metabolism
- Thyroid Hormone Action
Background:
- Congenital hypothyroidism (CH) requires timely treatment with L-thyroxine (L-T4).
- Thyroid hormones play a crucial role in regulating serum lipid profiles.
- The specific impact of L-T4 therapy on serum apolipoproteins in infants with CH is not fully characterized.
Purpose of the Study:
- To investigate the effects of L-T4 replacement therapy on serum apolipoprotein levels in infants with CH.
- To understand the relationship between thyroid hormone status and lipid metabolism in early life.
Main Methods:
- Prospective study of infants diagnosed with congenital hypothyroidism.
- Serum samples collected before and after initiation of L-T4 replacement therapy.
- Quantification of serum lipid profile components including total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), and high-density lipoprotein cholesterol (HDLC).
- Measurement of serum apolipoproteins: apo A-I, apo A-II, apo B, apo C-III, apo C-II, and apo E.
Main Results:
- Serum HDLC levels significantly decreased following L-T4 therapy.
- No significant changes were observed in TC and LDLC levels post-therapy.
- Serum concentrations of apolipoprotein A-I (apo A-I), apo C-III, and apo E significantly declined after L-T4 treatment.
- Serum apo B levels significantly increased after L-T4 therapy.
- Serum apo A-II and apo C-II levels remained unchanged.
Conclusions:
- In infants with CH, L-T4 replacement therapy leads to a reduction in serum apo A-I, a key component of HDLC.
- The decline in apo A-I may contribute to the observed decrease in serum HDLC concentrations after L-T4 therapy.
- Thyroid hormones significantly influence the serum apolipoprotein profile in infants, impacting lipid metabolism.
Abstract:
To further characterize the impact of thyroid hormones on the serum lipid profile, we studied serum apolipoproteins in infants with congenital hypothyroidism before and after L-thyroxine (L-T4) replacement therapy. Serum high-density lipoprotein cholesterol (HDLC) decreased after L-T4 therapy. Total cholesterol (TC) and low-density lipoprotein cholesterol (LDLC) levels did not change significantly after therapy. Two months after L-T4 replacement therapy, serum apolipoprotein A-I (apo A-I), C-III, and E declined and apo B increased significantly. No significant changes were observed for serum concentrations of apo A-II and C-II after L-T4 substitution. We conclude that in infants, thyroid hormone reduces serum levels of apo A-I, the principal protein component of HDLC, and this may contribute to the decline of serum HDLC concentrations after L-T4 replacement therapy.