STK31 and fibromyalgia: STK31 encodes a testis-specific protein kinase with unclear relevance to fibromyalgia; however, the variant is ~400 kilobases upstream of NPY (its sixth-nearest gene), an abundant neuropeptide that modulates appetite, circadian rhythm, anxiety, cardiovascular function, and immune responses63 and has both pro- and anti-nociceptive effects64.