Thyroxine treatment increases circulating levels of insulin-like growth factor binding protein-1: a placebo-controlled study.
OBJECTIVE
Thyroid hormones affect carbohydrate metabolism in the liver, and hepatic insulin-like growth factor binding protein-1 (IGFBP-1) participates in glucose counter-regulation, so we studied the effects of oral thyroxine on serum IGFBP-1.


METHODS
The study was performed on a placebo-controlled cross-over basis covering 3 months' thyroxine and 3 months' placebo administration.


METHODS
Eight patients taking anticonvulsant medication and four patients with hypothalamic hypothyroidism were given thyroxine, 150-200 micrograms daily for 3 months, or placebo.


METHODS
Serum IGFBP-1, sex hormone binding globulin, free T3 and free T4, TSH and IGF-I levels were measured after an overnight fast before treatment, and at the end of each 3-month period.


RESULTS
Anticonvulsant medication had no significant effect on serum IGFBP-1. After 3 months' thyroxine treatment the serum IGFBP-1 levels (69; 58-167 micrograms/l; median and interquartile range, respectively) were significantly higher than those after placebo treatment (44; 23-58 micrograms/l; P = 0.002), or the pretreatment levels (54; 19-81 micrograms/l, P = 0.005). The IGFBP-1 levels rose in all 12 patients after thyroxine treatment, the median rise being 2.1-fold compared to placebo levels. No change was found in serum IGF-I concentrations.


CONCLUSIONS
Oral thyroxine produces a rise in serum IGFBP-1 levels without a change in serum IGF-I concentration.
Angervo
M
M
First Department of Obstetrics and Gynaecology, Helsinki University Central Hospital, Finland.
Tiihonen
M
M
Leinonen
P
P
Välimäki
M
M
Seppälä
M
M
D000328:Adult; D000368:Aged; D002220:Carbamazepine / Q000627:therapeutic use; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000188:drug therapy; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D008875:Middle Aged; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013974:Thyroxine / Q000627:therapeutic use*
D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D012738:Sex Hormone-Binding Globulin; D002220:Carbamazepine; D007334:Insulin-Like Growth Factor I; D013974:Thyroxine