Biologic markers in blood reflecting thyroid hormone effect at peripheral tissue level in patients receiving levothyroxine replacement for hypothyroidism.
Plasma fibronectin, serum procollagen-III-peptide and sex-hormone binding globulin as not specific markers of thyroid hormone effect at peripheral tissue level were determined and their values were related with serum levels of TSH, free-thyroxine and triiodothyronine during levothyroxine sodium replacement therapy for hypothyroidism. Low levels of biologic markers characteristic of hypothyroidism were normalized in consequence of hormone replacement and a negative correlation between their serum levels and TSH concentration was demonstrated in most subjects. However, in some patients a discrepancy in the response to levothyroxine between the pituitary and other target organs could be revealed. Additional evidence was disclosed that the pituitary thyrotroph sensitizes a minor decrease in serum thyroxine level, which would not be recognized by other target organs. Furthermore, it was revealed that during L-T4 replacement therapy in a large fraction of patients with subnormal serum TSH concentration blood levels of the measured markers often exceeded the upper limit of the normal range indicating the possibility of "tissue"-thyrotoxicosis beside the pituitary in other target organs, too. According to the present study which takes into consideration markers reflecting end-organ responsiveness to thyroid hormones it is recommended to adjust the dose of levothyroxine to maintain serum TSH in the normal range. For patients with subnormal TSH concentration a close follow-up is obligatory and in case od concomitantly raised free-thyroxine level the reduction of the levothyroxine dosage is proposed.
Földes
J
J
First Department of Medicine, Semmelweis University Medical School, Budapest, Hungary.
Tarján
G
G
Bános
C
C
Németh
J
J
Varga
F
F
Büki
B
B
D000328:Adult; D015415:Biomarkers / Q000097:blood*; D005260:Female; D005353:Fibronectins / Q000097:blood; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000188:drug therapy*; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood; D011347:Procollagen / Q000097:blood; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*; D014284:Triiodothyronine / Q000097:blood
D015415:Biomarkers; D005353:Fibronectins; D010446:Peptide Fragments; D011347:Procollagen; D012738:Sex Hormone-Binding Globulin; C041876:procollagen Type III-N-terminal peptide; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine