Congenital goiter (cog), a new autosomal recessive mutation in mice, has been mapped to the central region of chromosome 15. Young adult mutant mice are characterized by a reduced rate of growth, mild anemia, hypothyroidism, as indicated by significantly lower total serum T4 and T3, and elevated serum TSH. Thyroids from mutant mice are hypertrophied, deficient in colloid, show a reduced accumulation of iodine that is partially susceptible to perchlorate ion discharge, have modestly elevated serum immunoreactive thyroglobulin (Tg) levels, but are markedly deficient in glandular immunoreactive Tg content. Thyroid hormone therapy corrects the growth deficiency and prevents the thyroid hypertrophy resulting from excessive stimulation by TSH. These findings suggest that the cog mutant gene results in primary hypothyroidism in response to either defective synthesis or processing of Tg
