Abstract |
The present study was undertaken to investigate the possible regulatory effect of chronic exposure to human growth hormone (hGH), in patients with acromegaly, on growth-hormone-binding protein (GH-BP). Nineteen patients with active acromegaly, before, during or after treatment, comprised the subjects of this study. Serum GH was measured by radioimmunoassay and GH-BP by a binding assay with dextran-coated charcoal separation. The specific binding of [125I]hGH (1 ng) obtained with 50 microliters serum was expressed as a percentage of total cpm. To evaluate the impact of the lower GH-BP on GH activity, we studied the effect of acromegalic serum on hGH displacement of [125I]hGH binding to GH receptors in rabbit liver membranes. Compared to normal controls (11.43 +/- 0.37%), the acromegalic patients had low serum levels of GH-BP (5.45 +/- 0.40%; p < 0.001), which correlated negatively with serum GH levels (p < 0.01). In 7 patients, GH-BP normalized within 2-3 months of successful therapy. The lower GH-BP was due to a reduction in binding capacity, whereas binding affinity remained unchanged. Acromegalic serum, with its low GH-BP, resulted in a shift to the left of the GH displacement curve when compared with normal human sera: IC50 values were 7.47 +/- 0.29 and 11.19 +/- 0.84 ng (p < 0.02) for acromegalic and normal human sera, respectively. We conclude that acromegaly is characterized by low levels of GH-BP due to a decrease in serum-binding capacity. The decrease in GH-BP may render the acromegalic serum GH relatively more active in the GH receptor assay.
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Authors | T Amit, S Ish-Shalom, B Glaser, M B Youdim, Z Hochberg |
Journal | Hormone research
(Horm Res)
Vol. 37
Issue 6
Pg. 205-11
( 1992)
ISSN: 0301-0163 [Print] Switzerland |
PMID | 1292973
(Publication Type: Journal Article)
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Chemical References |
- Carrier Proteins
- Receptors, Somatotropin
- Insulin-Like Growth Factor I
- Growth Hormone
- somatotropin-binding protein
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Topics |
- Acromegaly
(blood, therapy)
- Adult
- Aged
- Animals
- Biological Assay
- Carrier Proteins
(blood)
- Female
- Growth Hormone
(blood)
- Humans
- In Vitro Techniques
- Insulin-Like Growth Factor I
(metabolism)
- Kinetics
- Liver
(metabolism)
- Male
- Middle Aged
- Rabbits
- Receptors, Somatotropin
(metabolism)
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