Fibromyalgia Syndrome (FMS); It is a chronic condition characterized by widespread body pain, sleep disturbance, fatigue, impaired cognitive functions, and anxiety (1). FMS; chronic fatigue syndrome, interstitial cystitis, irritable bowel syndrome, temperomandibular joint dysfunction, myofascial pain, functional dyspepsia, restless leg syndrome and posttraumatic stress disorder are among central sensitization syndromes (2,3).

Etiology and pathogenesis in fibromyalgia have not been fully elucidated. Many mechanisms contribute to the formation of FMS. Many evidence has been found for dysfunction of the central and autonomic nervous system, immune system, cytokines, neurotransmitters and hormones, which are thought to play a role in the disease.

Since increasing systemic inflammation is thought to have a role in the etiopathogenesis of FMS, there are increasing numbers of studies focusing on this aspect of fibromyalgia.

Neutrophil / lymphocyte ratio (NLR) and platelet / lymphocyte ratio (PLR) in peripheral blood are simple markers of systemic inflammatory response.

Another factor thought to have a role in etiopathogenesis is autonomic nervous system dysfunction. It has been found that there is autonomic dysfunction in the sympathetic nervous system in patients with FMS. Sympathetic skin response measurements are frequently used electrophysiological methods to evaluate the functionality of the sympathetic nervous system, which is a component of the autonomic nervous system.

In addition, vitamin D deficiency is common in FMS patients. In a study, inadequate vitamin D levels were found in 45% of fibromyalgia patients.

When a literature review is performed, it is seen that electrophysiological studies are performed to evaluate autonomic dysfunction in patients with fibromyalgia. No studies were found showing the relationship between vitamin D levels and inflammatory parameters in patients with fibromyalgia and electrophysiological findings. In our study, it was aimed to compare the autonomic dysfunction of fibromyalgia patients with healthy volunteers by electrophysiological evaluation and to investigate the relationship between vitamin D levels and inflammatory parameters in fibromyalgia patients and the data obtained from electrophysiological studies. In this way, we aimed to contribute to a better understanding of the physiopathology of fibromyalgia patients with autonomic dysfunction.

Inclusion Criteria:

• 18-65 years old To be diagnosed with FMS according to the criteria of American College of Rheumatology (ACR) 2010 Confirmed diagnosis of FMS according to American College of Rheumatology (ACR) 2016 criteria

Exclusion Criteria:

• Presence of acute infection Diabetes Mellitus B12 deficiency Hypothyroidism Inflammatory-rheumatological disease presence A history of malignancy Major psychiatric disorder Dementia, etc. diseases that may cause loss of cognitive functions