Effect of thyroid function on concentrations of lipoprotein(a)
The effect of thyroid hormones on concentrations of lipoprotein(a) [Lp(a)] was analyzed in 60 patients with active thyroid dysfunction (hyperthyroidism 30 cases, hypothyroidism 32 cases, and 2 cases with opposite changes) and after normalization of the thyroid state. Treatment of hyperthyroidism increased the mean Lp(a) concentrations by 60% (from 73 to 102 mg/L, P < 0.002); at the same time, low-density lipoprotein cholesterol (LDL-C) increased by 53% (from 2.6 to 3.7 mmol/L, P < 0.0001) and apolipoprotein B (apo B) by 35% (from 0.91 to 1.17 g/L, P < 0.0005). In hypothyroidism, the opposite changes were observed: mean Lp(a) decreased from 136 to 114 mg/L (10%, P < 0.02), LDL-C from 4.6 to 3.9 mmol/L (13%, P < 0.01), and apo B from 1.51 to 1.20 g/L (14%, P < 0.01). Although the changes in Lp(a) concentrations did correlate with changes of LDL-C during treatment of hyperthyroidism (r = 0.43, P < 0.05), and with changes in apo B during thyroxine-substitution therapy for hypothyroidism (r = 0.46, P < 0.05), we observed no associations between Lp(a) and LDL-C or apo B in the euthyroid state. These data cannot rule out the possibility that the thyroid hormone-induced increase in LDL-C receptor activity was responsible for the decreased concentrations of Lp(a) in hyperthyroidism. Given that LDL-C is approximately 30% of the Lp(a) molecule but the changes in Lp(a) concentrations are comparable with those in LDL-C (60% vs 53%), and given that Lp(a) is metabolized by an LDL-C-receptor-independent pathway, the present data suggest a direct effect of thyroid hormones on Lp(a) synthesis.
Engler
H
H
Institute of Clinical Chemistry and Hematology, State Hospital, St. Gallen, Switzerland.
Riesen
W F
WF
D000328:Adult; D000368:Aged; D001055:Apolipoproteins B / Q000378:metabolism; D008078:Cholesterol, LDL / Q000097:blood; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood* / Q000532:radiotherapy / Q000628:therapy; D007037:Hypothyroidism / Q000097:blood* / Q000628:therapy; D017270:Lipoprotein(a) / Q000097:blood*; D008297:Male; D008713:Methimazole / Q000627:therapeutic use; D011247:Pregnancy; D011441:Propylthiouracil / Q000627:therapeutic use; D013974:Thyroxine / Q000627:therapeutic use
D001055:Apolipoproteins B; D008078:Cholesterol, LDL; D017270:Lipoprotein(a); D008713:Methimazole; D011441:Propylthiouracil; D013974:Thyroxine