Lipoprotein alterations, hepatic lipase activity, and insulin sensitivity in subclinical hypothyroidism: response to L-T(4) treatment.
Subclinical hypothyroidism (sH) has been associated with atherosclerotic cardiovascular disease even in the absence of hypercholesterolemia.


OBJECTIVE
Our study was designed to assess the hypothesis that other pro-atherogenic parameters, such as qualitative lipoprotein changes and insulin resistance, might be present in sH.


METHODS
Twenty-one sH women were compared to 11 female controls matched for body mass index, menopausal status, and age. Before and after 6 months of levothyroxine (L-T(4)) treatment, we determined total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides (TG), apoB levels, hepatic lipase (HL) activity in postheparin plasma samples, the chemical composition and copper-induced oxidation in isolated LDL and homeostasis model assessment (HOMA), quantitative insulin sensitivity check index, and insulinogenic index.


RESULTS
Lipid profiles were similar between the two groups. No differences in LDL oxidability or the insulin sensitivity assessment parameters were found. HL activity was significantly lower in the sH patients: median (range), 13.1 (2.5-26.7) vs. 18.7 (7.9-28.1) micromol free fatty acids/mL, p < 0.04. The LDL-cholesterol/LDL-TG ratio was decreased in sH: 3.9 (1.8-5.5) vs. 4.7 (3.5-6.8), p < 0.02. HL negatively correlated with thyroid-stimulating hormone (TSH) levels (r = - 0.504, p < 0.01) and positively with LDL-cholesterol/LDL-TG (r = 0.46, p < 0.02). Posttreatment results for all these parameters did not differ significantly compared to baseline.


CONCLUSIONS
Increased levels of TSH are associated to a decrease in HL activity, explaining our findings of an LDL particle rich in TG. This qualitative lipoprotein alteration suggests a pro-atherogenic pattern in sH. Treatment with L-T(4), however, did not correct the basal lipid derangement.
Brenta
Gabriela
G
Division of Endocrinology and Metabolism, Hospital Francés de Buenos Aires, Buenos Aires, Argentina.
Berg
Gabriela
G
Arias
Pablo
P
Zago
Valeria
V
Schnitman
Marta
M
Muzzio
Maria Luz
ML
Sinay
Isaac
I
Schreier
Laura
L
D000328:Adult; D000368:Aged; D008078:Cholesterol, LDL / Q000097:blood; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy* / Q000378:metabolism; D007333:Insulin Resistance; D008049:Lipase / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008875:Middle Aged; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use*; D014280:Triglycerides / Q000097:blood
D008078:Cholesterol, LDL; C504173:LIPC protein, human; D008077:Lipoproteins, LDL; D014280:Triglycerides; C099252:oxidized low density lipoprotein; D013972:Thyrotropin; D008049:Lipase; D013974:Thyroxine