Type II 5′-Deiodinase (5′DII) is a key element in the maintenance of peripheral thyroid hormone homeostasis through the regulation of local T4 to T3 conversion in pituitary, brain, brown adipose tissue and placenta. The cDNA containing the coding region of the human 5′DII (HDII) has been recently cloned from infant brain. In the present paper we report the genomic structure, chromosomal localization and restriction map of the coding region of HDII. The presence of a single intron located at codon 75 was demonstrated using a PCR-based strategy; the exon–intron junctions were then cloned and partially sequenced. Chromosomal localization was performed by radiation hybrid mapping. This study demonstrated that the entire coding region of the HDII gene is contained in two exons spliced at codon 75 by a 7.4 Kb intron and that the HDII chromosomal location is 14q24.3. These data will allow further studies of the role of HDII in the pathophysiology of thyroid homeostasis.
