Altered Serum Oxytocinase and Enkephalin-Degrading Aminopeptidase Activities in Patients With Fibromyalgia.

Our findings show that serum oxytocinase activity is increased in patients with FM, which could alter the metabolism of peptides with analgesic effects such as oxytocin and enkephalins. The determination of serum oxytocinase activity may aid in FM diagnosis. Additionally, we have identified a subpopulation of FM patients with abnormally low serum EDA activity.