New Form Of Inherited Dwarfism In Large Pakistani Family Caused By Genetic Mutation In A Pituitar...( deficiency with abnormal levels of in...)

deficiency, with abnormal levels of insulin-like growth factors. Subsequent genetic analysis linked the unique form of dwarfism to an inactivating mutation in the gene for the growth hormone-releasing hormone receptor (GHRH-R), which triggers pituitary growth hormone secretion and growth in humans. The mutated GHRH-R causes growth hormone deficiency due to GHRH resistance.

Molecular genetic testing showed that inheritance of the dwarfism trait is transmitted in an autosomal recessive manner; i.e., the mutated gene, located on chromosome 7, must be carried by both parents for the disorder to manifest. Those who had only one copy of the gene (heterozygous) had mild biochemical GHRH-R abnormalities but only minimal or no growth retardation.

Four of the affected males in the group were later brought to the Medical School for further evaluation, which included magnetic resonance imaging of the pituitary, bone density testing and additional hormone level assessments. Results of the tests are forthcoming.

Dwarfism of Sindh, as this syndrome is now called, is the human genetic counterpart to the little (lit/lit) mouse. This mouse also has a mutation in the GHRH-R, causing GHRH resistance, an underdeveloped pituitary, growth hormone deficiency and a dwarfed body. The mouse also has decreased brain weight, a finding consistent with the small head circumference in the human dwarfs.

Baumann said these findings may facilitate studies of milder mutations in the GHRH-R or related genes as a potential cause of some growth disorders, as well as a better understanding of the genetic regulation of growth.

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Contact: Elizabeth Crown
e-crown@nwu.edu
312-503-8928
Northwestern University
3-Nov-1998

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