Effect of thyroid hormone on the serum level of somatomedin A.
The effect of thyroid hormone on the serum level of somatomedin A was studied using a radioreceptor assay for somatomedin A. In 13 patients with hyperthyroidism, the mean level of somatomedin A was 0.06 +/- 0.05 U/ml, which was within the normal range. Low levels were found in 19 patients with primary hypothyroidism with a mean of 0.39 +/- 0.04 U/ml. After treating these patients with thyroxine, the serum somatomedin A levels returned to the normal range. There was a significant correlation between the somatomedin A level on one hand and T3 (r = 0.49) and T4 (r = 0.55) level on the other. The serum level of somatomedin A did not decrease for 7 days after thyroidectomy nor increase after treating hypophysectomized rats with 2 microgram of thyroxine for 14 days. However, the effect of growth hormone on serum somatomedin A was augmented 42.2% by the combined administration of the same amount of T4 for 7 days. There was a positive correlation between the serum level of somatomedin A and the percentage increase in body weight (4 = 0.73). These data suggest that thyroxine potentiates the effect of GH on synthesis and/or the secretion of somatomedin A.
D000328:Adult; D000368:Aged; D000818:Animals; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood; D007016:Hypophysectomy; D007037:Hypothyroidism / Q000097:blood; D007335:Insulin-Like Growth Factor II; D008297:Male; D008875:Middle Aged; D011869:Radioligand Assay; D051381:Rats; D013002:Somatomedins / Q000097:blood*; D013963:Thyroid Hormones; D013965:Thyroidectomy
D013002:Somatomedins; D013963:Thyroid Hormones; D007335:Insulin-Like Growth Factor II