Thyroxine withdrawal is accompanied by decreased circulating levels of insulin-like growth factor-binding protein-1 in thyroidectomized patients.
We carried out a study on the effect of T4 withdrawal on serum insulin-like growth factor-binding protein-1 (IGFBP-1) levels in 10 thyroidectomized patients with papillary thyroid cancer receiving T4 replacement therapy. As controls we also measured serum sex hormone-binding globulin (SHBG) levels, known to be regulated by T4. Each patient acted as his/her own control, studied both before and 30 days after T4 withdrawal. On the average, the IGFBP-1 level decreased by 36% from 66 +/- 9 to 44 +/- 8 micrograms/L (mean +/- SE; P = 0.0007) during T4 withdrawal. The SHBG level decreased by 47% from 78 +/- 17 to 46 +/- 13 nmol/L (P = 0.0001). The fasting insulin levels were unaffected by T4 withdrawal. There also was an 18% decline in the serum IGF-I concentration after T4 withdrawal (P = 0.011). It is concluded that in athyreotic patients receiving T4, withdrawal of the drug decreases serum IGFBP-1 and SHBG concentrations and IGF-I levels. In view of the possible role of IGFBP-1 in glucose counterregulation, these results indicate a novel mechanism by which T4 may exert its metabolic action on liver carbohydrate metabolism.
Angervo
M
M
First Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Finland.
Toivonen
J
J
Leinonen
P
P
Välimäki
M
M
Seppälä
M
M
D000328:Adult; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013002:Somatomedins / Q000378:metabolism; D013375:Substance Withdrawal Syndrome / Q000097:blood*; D013965:Thyroidectomy; D013974:Thyroxine / Q000009:adverse effects*
D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D012738:Sex Hormone-Binding Globulin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013974:Thyroxine