Relationship of Nocturnal Melatonin Levels to Duration and Course of Multiple Sclerosis

Abstract

Multiple sclerosis (MS) is the most common of the demyelinating diseases of the CNS. The clinical course and prognosis of the disease are variable. Characteristically, the illness tends to progress in a series of relapses and remissions. Over the years there is a tendency for the patient to enter a phase of slow and steady deterioration of neurologic function. In about 10%-20% of patients, the course of the disease is not punctuated by a fluctuating course, but rather by an inexorable progression from the onset. The pineal gland has been implicated recently in the pathogenesis and clinical course of MS. Since MS is generally a chronic progressive disorder, we predicted an association between duration of illness and the activity of the pineal gland. To investigate this hypothesis further, we studied nocturnal plasma melatonin levels in relation to duration of illness in a cohort of 32 MS patients (4 men, 28 women; mean age: 41.1 years; SD = 11.1; mean duration of illness: 13.1 years; SD = 12.4) randomly selected from consecutive hospital admissions to a Neurology service for exacerbation of symptoms. For the purpose of comparison, we also studied in the sample serum prolactin levels. The cohort included 7 patients in whom the duration of illness since onset of first neurological symptoms was ≤5 years (mean: 3.0 years ± 1.1) and a cohort of 25 patients in whom the duration of illness was >5 years (mean: 15.6 years ± 12.7). The mean melatonin level in the patients with a duration of illness of >5 years was significantly lower compared to those patients whose duration of illness was ≤5 years (54.0 pg/ml ± 35.0 vs. 31.9 pg/ml ± 21.6; p <. 05). However, serum prolactin levels did not differ significantly between the groups and did not correlate with melatonin levels. These findings demonstrate a specific association between nocturnal melatonin secretion and duration of clinical symptoms of MS and suggest that the activity of the pineal gland may decline with progression of the disease. Furthermore, we propose that the steady progression of the disease may be linked partially to a progressive failure of the pineal gland to exert an immunosuppressant effect and facilitate neurologic recovery.

Keywords:

• Multiple sclerosis
• melatonin
• pineal gland.