Objective : Multiple sclerosis (MS) is a common neurological disease deeply linked with the immune-inflammatory disorders whereas the term (multiple) mostly refers to the multi-focal zones of Inflammation caused by lymphocytes and macrophages infiltration besides oligodendrocytes death. Accordingly , the dysfunctional immune system able to damage myelin ( a pivotal component of the central nervous system ) which responsible for communication among neurons. The aim of the present study is to innovate a biochemical relationship between MS and thyroid hormones (THs) by highlighting immunological responses and also to examine the action of Interferon beta (IFNβ) drug on thyroid hormone (THs) and thyroid stimulation hormone (TSH). Materials and methods: Sixty (60) Iraqi women in the age ranged (36-43) years were enrolled in the present study, (30) of them were MS patients and the other (30) were healthy. Anyway, the protocol of the study involved four groups: G1 is a healthy control group, G2 involved untreated MS patients, G3 included the MS patients treated with IFNβ for (6) weeks and G4 composed of the same patients treated with IFNβ for (12) weeks. THs (T4 and T3) and TSH levels were determined in sera of all groups. Results: Data of the present study have reported that T4 level was highly significant increase in sera of G2 compared with G1 while it was significant and highly significant decreased in G3 and G4 respectively compared with G2, the difference between G4 and G1 and also between G4 and G3 was significant. T3 level was highly significant increase in sera of G2 compared with G1 but it was highly significant decreased in G3 and G4 compared with G2, the difference between G4 and G1 was non-significant while the difference between G4 and G3 was significant. Conversely, TSH level was highly significant decreased in G2 compared with G1 but it was highly significant increase in G3 and G4 compared with G2, the difference between G4 and G1 and also between G4 and G3 was highly significant. Conclusions : Interestingly , the present study is the first in Iraq reporting that MS may be a key risk factor for hyperthyroidism and also the first suggesting that IFNβ regulates THs biosynthesis via novel immuno-neuro-enzymological mechanisms regarding thyroid peroxidase (TPO) and iodothyronine deiodinase 1 (D1), meanwhile the present study indicates that IFNβ has an indirect antioxidant activity. Moreover, the present study provides a definite clarification for the changed NF kappa B level in MS. Remarkably, the present study reveals that IFNβ is more potent on T3 than T4 while it has less action on TSH.