[An alternatively spliced form of the human thyrotropin receptor transcript].

An alternatively spliced form of the human thyrotropin receptor (hTSHR) mRNA transcript, which has previously been detected on Northern blot analysis of human thyroid cells, was cloned. The smaller hTSHR cDNA, designated hTSHR cDNA-I, is approximately 1 kb in size and encodes a protein of 253 amino acids. Comparison of the nucleotide sequence of hTSHR cDNA-I with available hTSHR genomic sequence data reveals that the cDNA-I contains exons 1-8 and an unidentified DNA tract, presumably an intron. Thus, the hTSHR cDNA-I encodes the N-terminal half of the extracellular domain of the hTSHR (approximately 60%). The truncated TSHR-I may be secreted and function as a TSH binding protein.