Laron-type dwarfism is an autosomal recessive genetic disorder that is characterized by high levels of growth hormone and low levels of insulin-like growth factor I in the circulation. Several lines of evidence suggest that this disease is caused by a defect in the growth hormone receptor. In order to analyze the receptor gene in patients with Laron-type dwarfism and with other growth disorders, we have first determined the gene structure in normal individuals. There are nine exons that encode the receptor and several additional exons in the 5' untranslated region. The coding exons span at least 87 kilobase pairs of chromosome 5. Characterization of the growth hormone receptor gene from nine patients with Laron-type dwarfism shows that two individuals have a deletion of a large portion of the extracellular, hormone binding domain of the receptor gene. Interestingly, this deletion includes nonconsecutive exons, suggesting that an unusual rearrangement may have occurred. Thus, we provide direct evidence that Laron-type dwarfism can result from a defect in the structural gene for the growth hormone receptor.
