RAPID DETECTION OF A POINT MUTATION IN THYROID-STIMULATING HORMONE BETA-SUBUNIT GENE CAUSING CONGENITAL ISOLATED THYROID-STIMULATING HORMONE DEFICIENCY

Previous study showed that congenital isolated TSH deficiency in Japan is resulted exclusively from a G-A transition at nucleotide 145 in exone 2 of the TSH-beta-subunit gene. All reported cases were from the inbred in Shikoku Island. We describe here a 10-year-old boy with hereditary TSH deficiency in the same area. The patient was born with a weight of 3,225 g to non-consanguineous parents. Evaluation at age 2 months revealed typical manifestations of cretinism without goiter. Serum T4, T3, and TSH values were 2.53-mu-g/dl, 107 ng/dl, and 0.5-mu-U/ml, respectively. A TRH stimulation test showed no increment of serum TSH value. Other anterior pituitary hormone levels were all within the normal range, Two oligonucleotide primers T1a and T1b were synthesized according to the sequence data. Amplified 169 bp nucleotides in exon 2 of the TSH-beta gene with this primer set were digested with MaeI. Both the phenotypically normal brother and normal controls showed only the 169 bp fragment, whereas the proband showed 140 and 29 bp fragments and both parents showed three fragments; 169, 140, and 29 bp. These results were consistent with the point mutation of TSH-beta gene in Japanese patients with congenital isolated TSH deficiency. Our PCR method with MaeI digestion contributes to the rapid detection of the homozygous patient and the heterozygous carrier.