We previously reported that the FGFR4-R388 allele modulates GH levels and is associated with larger pituitary tumor size in patients with acromegaly; STAT3 tyrosine phosphorylation is an inhibitory signal of GH secretion in pituitary cells and phosphorylated STAT3 serine in mitochondria plays a crucial role in cell proliferation [40]. This evidence concerns the gene FGFR4 and pituitary tumor.