Clinical Utility of Melatonin in Fibromyalgia Diagnosis

Fibromyalgia syndrome (FMS) is a chronic disease with an unknown etiology, which is characterized by reduced pain threshold (hyperallgesia) & pain with normally innocuous stimuli (allodynia).This diffuse pain is often disease associated with wide range of other symptoms including fatigue, sleep disturbance, stiffness& more.FMS often occur concomitantly with other rheumatologic disease such as rheumatoid arthritis(RA), systemic lupus erthymatosus(SLE).


INTRODUCTION:
The key symptoms of fibromyalgia syndrome (FMS) are chronic, widespread pain associated with cognitive dysfunction, sleep disturbances and physical fatigue [8,24] . Also it is a clinical condition in which hyperalgesia, allodynia and stiffness of the body are found [17] . Familial component, environmental factors, endocrinological and neurotransmitter changes, and psychological factors are suggested to contribute in the development of FMS [ 1] . Most patients with fibromyalgic syndrome (FMS) complain of sleep disturbances, fatigue, and pain. These symptoms might be a consequence of changed melatonin (MT) secretion, since MT is known to have sleep promoting properties.
Altered functioning of the hypothalamic-pituitary-adrenal axis and altered melatonin Production might modulate the circadian rhythm in patients with rheumatoid arthritis.
It has been reported that patients with this syndrome have a higher serum concentration of serotonin autoantibodies not only when compared with healthy controls [10] , but also when compared with patients with other rheumatic diseases [11] . Also low serum levels of both serotonin [23,26] and its precursor tryptophan [20] appear to prevail in patients with FMS.
Melatonin (MT) is a very popular neurohormone frequently investigated in recent years. MT was suggested to be effective in the etiology and treatment of some diseases. MT is synthesized primarily in the pineal gland [22].

OBJECTIVE:
The aim of this study was to assess serum melatonin level & investigate it ' s correlation to the clinical utility of fibromyalgia syndrome (FMS).

PATIENTS AND METHODS:
Fifty five patients, fulfilling the American Colleague of Rheumatology (ACR) criteria for FMS [24] were selected from the in-and out-patients' clinics of the Rheumatology and Immunology department at Benha teaching Hospital. Twenty apparently healthy subjects of comparable age and sex to FMS patients were included as a control group.
All patients underwent full history taking and clinical examination including assessment of disease activity using the 2010 ACR FMS criteria [24] .
A patient satisfies diagnostic criteria for fibromyalgia if the following 3 conditions are met: 1) Widespread pain index (WPI) >7 and symptom severity (SS) scale score >5 or WPI 3-6 and SS scale score >9.
2) Symptoms have been present at a similar level for at least 3 months.
3) The patient does not have a disorder that would otherwise explain the pain.

WIDESPREAD PAIN INDEX:
1) WPI: note the number areas in which the patient has had pain over the last week. In how many areas has the patient had pain Score will be between 0 and 19. • All patients subjected to the following investigations: -Rheumatoid factor (RF), -Anti nuclear antibodies (ANA)and anti-DNA antibodies by ELISA.
-MELATONIN DETERMINATION: Sera were collected from patients and controls and stored at -20°C until use. Melatonin was quantitatively determined in the human serum by the enzyme linked immunosorbent assay (ELISA) supplied by Cusabio (Catalog No CSB-E08132h). An antibody specific to MT was bound to micro wells. Samples are then added to the micro wells with a biotin-conjugated antibody specific for Melatonin (MT) and avidin conjugated to Horseradish Peroxidase (HRP) is added to each micro wells and incubated. Then a TMB (3,3´,5,5´tetramethyl-benzidine) substrate solution is added to each well. Only those wells that contain MT, biotin-conjugated antibody and enzyme-conjugated avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wave lenght of 450 nm ± 2nm.The concentration of melatonin is then determined in the samples.

STATISTICAL ANALYSIS:
Statistical analysis of the results were carried out using SPSS software statistical computer package version 14.0(SPSS Inc.,IL), data expressed as Mean ± SD or SEM Statistical differences between groups were determined by student's unpaired t-test. Significance was taken to be p≤ 0.05. Correlation coefficient (r) was used for measuring the relationship between two variables.
Group I: included 25 patients with FMS, with a mean age of 33.2± 13.8 years, mean disease duration of 5.7 ± 1.6 years and mean MT level of 21.32 ± 3.86 (mean ±SD).
-Group II: included 30 FMS patients, with a mean age of 34.6 ± 13.1 years, a mean disease duration of 5.6± 1.5 years and mean MT level of 138.1 ± 13.16.
-The control Group Included 20 subjects, all are females with age of 36.2 ± 14.6 years. This group matched FMS patients as regards to age and sex, Table (1).

MT level and Clinical features of FMS patients.
In FMS patients, the titers of MT varied between 10.7 and 120.4 pg/ml, with a mean of 86.5 ± 8.01 pg/ml.

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In the control group, the titers of MT varied between 18.8 and 41.4 pg/ml, with a mean of 30.9 ±8.1 pg/ml.
-There is a statistical significant difference was observed between MT level in FMS patients and the control group (p<0.011).

DISCUSSION:
Fibromyalgia is a common rheumatologic disorder that is under diagnosed. Using the 1990 ACR classification criteria, the prevalence of fibromyalgia in the general population is reported to be higher than in women than men [20] .
There is a higher prevalence in females because females produce more neurotransmitters that increase pain signals and fewer neurotransmitters that decrease pain signals than males, so in our study we observe that all patients are females [15] .
Studies suggested that when endogenous tryptophan is depleted, there is a dramatic drop in the synthesis of serotonin in females [19] , this make females being more sensitive to pain [26] .
The syndrome may coexist with other rheumatic diseases such as rheumatoid arthritis and systemic lupus erthymatosus in this case fibromyalgia be considered a secondary type [2] .
Disturbances in melatonin secretion have been proposed to be part of the pathophysiology leading to FMS.
The circadian rhythm [12] and secretion of melatonin have been examined in patients with FMS [13] . No significant differences were observed in the 24-hr plasma melatonin, between ten subjects and ten controls [12] .
We found that MT level was lower in primary FMS patients compared with healthy age and sex-matched subjects. The clinical implication of this finding is disturbed sleep at night and, as consequence, daytime sleepiness, fatigue and increased pain. Sleep disturbances, fatigue and cognitive dysfunction, are symptoms present in almost patient with FMS [8,16] , including those in this study.
In our study, MT levels of FMS patients were found to be lower than control group. There was correlation between the MT levels and pain, fatigue, and sleeping disorders. Our results weren't agree with the study of Press et al, Senel et al& Klerman [12,19,21] .
In concordance to the work included an eight patients with FM and eight controls, the concentration of melatonin in plasma and urine was found to be significantly lower in patients with FM [23] this agree with our data. But, Korszun et al. [13] however, reported that the melatonin concentration in urine was elevated in patients with FM when compared to controls.
Some authors had reported that patients with depression have decreased secretion of MT and increased secretion of cortisol [3] . As most FMS patients show signs of depression, a decreased MT level may explain their symptoms.
Decreased MT synthesis may be brought about by impaired provision of tryptophan. The amino acid tryptophan transforms into serotonin in the pineal gland, which then transforms into MT hormone. The decrease in serotonin as a result of the decrease in the absorption of tryptophan in FMS patients was suggested to be responsible for the decrease in MT synthesis, and accordingly that this may result in the abnormal sleeping pattern and typical FMS pain [9] .
For patients with rheumatoid arthritis (RA), social disadvantage, psychological distress and RA severity predicted future development of FMS [3] .
Many studies [5] confirmed that melatonin levels are increased in rheumatoid patients compared with sex and age matched healthy controls. Melatonin has been reported to stimulate the production of IL6 and Th1 related proinflammatory cytokines such as IL12, IL1&IL2, which are involved in the pathophysiology of rheumatoid arthritis [6] .
Melatonin is synthesized in human bone marrow cells [4] However, it has been found to be present at a rather high concentration in synovial fluid from rheumatoid patients, and recently it has been reported that synovial macrophages from rheumatoid patients have specific binding sites for melatonin [14] .
The levels of plasma melatonin were highest in SLE patients Plasma melatonin levels did not correlate with measures of clinical disease activity [7] .
In this current study melatonin level was high in 2ry FMS patients, who are having RA & SLE associated with FMS compared with healthy age and sex-matched subjects. This agree with the studies that observed that MT levels are higher in RA & SLE patients [5] . Also in this study there is a correlation between MT level and clinical features of 2ry FMS such as sleep disturbance, fatigue & more.
Melatonin level didn ' t seem to play a role in secondary fibromyalgia (patients with FMS associated with other diseases such as RA, SLE) which may be included by other factors which should be investigated in the future.