International researchers, including a team at McGill University, have discovered a new cause for thyroid hormone deficiency, or hypothyroidism. This common endocrine disorder is typically caused by problems of the thyroid gland, and more rarely, by defects in the brain or the pituitary gland (hypophysis). However, a new cause of the disease has been discovered from an unsuspected source and was reported online on November 11, 2012 in the journal Nature Genetics. The scientists, led by McGill Professor Daniel Bernard, Department of Pharmacology and Therapeutics in the Faculty of Medicine, identified a new hereditary form of hypothyroidism that is more prevalent in males than in females. This sex bias shone a light on where to look for the underlying cause. "Our collaborators in the Netherlands had been following a family in which two cousins had an unusual syndrome of hypothyroidisim and enlarged testicles," said Professor Bernard. "Using state-of-the-art DNA sequencing technologies, we identified a mutation in a gene called immunoglobulin superfamily, member 1 (IGSF1), in both boys and their maternal grandfather. As one of few labs in the world studying this gene, we initiated a collaboration to determine whether the observed mutation might cause the disorder. At the time, the IGSF1 gene was known to be active in the pituitary gland, but its function was a mystery.
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