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Lower resting metabolic rate and basal body temperature of fibromyalgia patients compared to

Lowe, J.C., et al.: Lower resting metabolic rate and basal body temperature of fibromyalgia patients compared to matched healthy controls.

Thyroid Science. 1:CLS1-24, 2006.

ABSTRACT. Introduction: All symptoms and most bjectively verified abnormalities of fibromyalgia are common among patients with hypothyroidism or partial peripheral thyroid hormone resistance. In treatment trials, thyroid hormone therapy has reduced or eliminated fibromyalgia symptoms, and a long-term follow-up study showed that improvement with thyroid hormone therapy lasted 1-to-5 years. In a previous study by the authors, solicited female fibromyalgia patients had significantly lower resting metabolic rates and basal body temperatures than matched healthy controls. In this study, the resting metabolic rates and body temperatures of fibromyalgia patients previously evaluated at a specialty metabolic clinic were compared with healthy controls to whom they were matched.

Methods: Fifteen female fibromyalgia patients and 15 healthy females served as study subjects. Patients were clinical cases selected to match controls by sex, age, weight, and activity level. Resting metabolic rate (RMR) was measured by indirect calorimetry (MedGem), basal body temperature with digital thermometers, and body composition by bioelectrical impedance. The mean measured resting metabolic rate (mRMR) was compared to percentages of the mean predicted RMR (pRMR) by two methods: fat-free weight (Sterling-Passmore equation: SP) and sex, age, height, and weight (Harris-Benedict and Mifflin-St. Joer equations: HB and MSt.J). Measurements were taken during the follicular phase of subjects menstrual cycles.

Results: Patients had a lower mean mRMR (939.70 216.04 kcal/d vs 1293.40 166.34 kcal/d, p = 0.00001) and lower mRMRs as percentages of pRMRs (SP: -26.91 13.36% vs -6.826 12.55%, p < 0.0001. HB: -32.45 13.48% vs -9.13 9.51%, p = 0.0001; MSt.J: -27.96 14.53% vs -5.089 11.30%, p = 0.0002). Age and fat-free weight accounted for 62% of variability in controls mRMRs. Fat-free weight, water as a percentage of body weight, and fibromyalgia symptom intensity accounted for 83% of the variability of patients mRMRs. Patients mean basal body temperature was significantly lower than that of controls (96.38 0.98 F vs 97.54 0.59 F, p = 0.001). Patients serum free T3 level was significantly lower than that of controls (3.18 0.559 vs 3.75 0.717 pg/mL, p = 0.023). Conclusions: The patient group had a lower mean mRMR and lower mRMR as percentages of pRMRs. Patients also had a significantly lower mean basal body temperature. Neither calorie restriction nor low fat-free weight accounted for patients lower RMRs. As in the previous study, fibromyalgia patients normal fat-free weight argues against low physical activity with poor physical fitness as the mechanism of their low RMRs. Free T4, free T3, and TSH levels did not correlate with fibromyalgia
measures or RMRs in either patient or control group. The lack of correlation does not rule out inadequate thyroid hormone regulation as the mechanism of the low RMRs
because studies have not shown that these laboratory values reliably predict RMR values.


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