Abstract. In a previous study, two subjects on stable dosages of the synthetic T3 product Cynomel found dosages of an dietary desiccated thyroid product (Hypo Support Formula or HSF) that maintained or improved clinical measurements provided by the previous dosages of Cynomel. The equivalence of HSF to Cynomel in maintaining the measurements was calculated to be 1 capsule of HSF to 15 mcg of Cynomel. In this study, another subject stable on Cynomel switched to the dosage of HSF previously calculated to effectively maintain the clinical and physiological measurements. Methods: A single-subject two-phase repeated-measures study design was used. The subject was a 24-year-old female. She had been stable for a year and a half on 100 mcg of Cynomel. She underwent 12 comprehensive metabolic evaluations on different days in the Cynomel phase. She then immediately switched from Cynomel to HSF and underwent 12 additional evaluations. The evaluations included four basal measures: metabolic rate (BMR), heart rate (BHR), axillary temperature (BAT), and blood pressure (BBP). Other measures were body composition, mean hypothyroid symptoms intensity, Zung’s depression scale, and pain distribution. Results: The subject’s physiological and clinical measurements, stable for 1.5 years on 100 mcg of Cynomel, were not statistically different when she used 7 capsules of HSF each day. The only significant differences in the subject’s measures were an increase in pain intensity and distribution during the HSF phase. Conclusion: For most measurements, including the BMR, BHR, and BAT, and hypothyroid symptoms intensity including depression, 7 capsules of HSF maintained the same values as 100 mcg of Cynomel. This outcome is consistent with that of the first study in which Cynomel and HSF were compared.