Effects of hypo or hyper-thyroidism on growth hormone-binding protein.
OBJECTIVE
Growth hormone (GH) receptors are influenced by the thyroidal state of experimental animals. It has been suggested that GH-binding protein (BP) might serve as an indirect measure of the GH receptors. The present study was undertaken to investigate the growth hormone binding protein in patients with hypo or hyperthyroidism.


METHODS
Patients included 42 adults with untreated hyperthyroidism (FT4 greater than 25 pmol/l; TSH less than 0.15 mU/l) and 29 adults and three children with untreated hypothyroidism (FT4 less than 10 pmol/l; TSH greater than 15 mU/l).


METHODS
Growth hormone binding protein was measured by a binding assay with dextran-coated charcoal separation. The specific binding of 125I-human GH (1 ng) obtained with 50 microliters serum was expressed as a percentage of the total c.p.m.


RESULTS
Growth hormone binding protein specific binding in hypothyroid adults and children was significantly lower than in their respective controls in both adults and children (P less than 0.001). In patients with FT4 levels greater than 40 pmol/l, the mean (+/- SEM) growth hormone specific binding (12.89 +/- 0.59%) was higher than in controls (P less than 0.05). However, in 15 hyperthyroid patients with levels of FT4 of 25-40 pmol/l, the mean growth hormone binding protein specific binding (11.22 +/- 0.76%) was not different from that in normal human subjects. The affinity constants (Ka) obtained by Scatchard analysis for the hypothyroid and hyperthyroid patients' sera were not significantly different from that for normal human sera. Binding capacity for the hypothyroid sera was significantly lower (P less than 0.02), while that of hyperthyroid sera was increased (P less than 0.001).


CONCLUSIONS
Growth hormone binding protein correlates positively with the thyroid status. It can be indirectly deduced that this reflects a similar relationship with the human GH receptor.
Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology.
T
T
Amit
P
P
Hertz
S
S
Ish-Shalom
R
R
Lotan
R
R
Luboshitzki
M B
MB
Youdim
Z
Z
Hochberg
D000328:Adult; D002352:Carrier Proteins / Q000378:metabolism*; D002648:Child; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood* / Q000378:metabolism; D007037:Hypothyroidism / Q000097:blood* / Q000378:metabolism; D007457:Iodine Radioisotopes; D013974:Thyroxine / Q000097:blood
D002352:Carrier Proteins; D007457:Iodine Radioisotopes; D013006:Growth Hormone; D013974:Thyroxine; C051815:somatotropin-binding protein