When a splice site mutation occurs in intron 2 of the gene that produces the parathyroid hormone, a parathyroid deficiency can prevail. In one particular study, a G to C substitution in the splice site of intron 2 produces a skipping effect in the messenger RNA transcript. The exon that is skipped possesses the initiation start codon to produce parathyroid hormone. Such failure in initiation causes the deficiency.