PubMed · 9172512
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S Takeda, K Inoue. 1997. [Glucagon-propranolol provocative test].. https://pubmed.ncbi.nlm.nih.gov/9172512/
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Laron syndrome, characterized by a short stature with raised serum levels of growth hormone but extremely low levels of insulin-like growth factor I, is caused by genetic defects of growth hormone receptor, including loss of functions of growth hormone receptor and abnormal growth hormone receptor acting in a dominant negative manner. This chapter focused on loss of functions of growth hormone receptor causing disruption of growth hormone binding and intracellular signalling. Most mutations and deletions have been found in extracellular domains of growth hormone receptor. Serum levels of growth hormone binding protein, cleaved from the extracellular portion of the growth hormone receptor, are typically decreased in most patients but are normal or high in some patients.
Truncated growth hormone receptor (GHR) mutations that lack the majority of the cytoplasmic domain have been identified in familial short stature and same truncated GHR isoforms generated by alternative splicing in a number of normal human tissues. The binding affinity of the truncated GHR was similar to that seen for the full-length receptor and the truncated GHR showed a much greater expression on the cell surface, which is consistent with lack of internalization. These truncated receptors function as dominant-negative inhibitors of the growth hormone (GH) signal and generate large amounts of GH binding protein (GHBP). Thus, truncated GHR isoform may be important as a physiological regulator of GH signaling in addition to providing a mechanism for the production of GHBP.