Effect of radioiodine treatment on muscle mass in hyperthyroid cats. (6th October 2022)

• Record Type: Journal Article
• Authors: Xifra, Pilar; Serrano, Sara I.; Peterson, Mark E.
• Is Part Of: Journal of veterinary internal medicine. Volume 36:Number 6(2022)
• Page Start: 1931
• Page End: 1941
• Publication Date: 2022-10-06
• Subjects: 131I -- cachexia -- feline -- muscle condition -- radioactive iodine -- sarcopenia -- thyroid gland -- ultrasound; Veterinary medicine -- Periodicals; 636.0896
• DOI: 10.1111/jvim.16560
• Languages: English
• ISSNs: 0891-6640

Abstract

Abstract: Background: Approximately 75% of hyperthyroid cats lose muscle mass as accessed with a muscle condition scoring (MCS) system. After treatment, MCS improves as the cats regain muscle mass. Objectives: To quantify the degree of muscle loss in hyperthyroid cats using ultrasonography and evaluate changes in muscle mass after treatment. Animals: Forty‐eight clinically normal cats and 120 cats with untreated hyperthyroidism, 75 of which were reevaluated after radioiodine‐131 therapy. Methods: Prospective cross‐sectional and before‐after studies. All cats underwent ultrasonography and measurement of epaxial muscle height (EMH), with subsequent calculation of vertebral and forelimb epaxial muscle scores (VEMS and FLEMS). A subset of hyperthyroid cats underwent repeat muscle imaging 6 months after treatment. Results: Untreated hyperthyroid cats had a lower EMH than did clinically normal cats (median [25th‐75th percentile], 0.98 [0.88‐1.16] cm vs 1.34 [1.23‐1.58] cm, P < .001). Seventy‐seven (64.2%) untreated cats had subnormal EMH. Similarly, compared to normal cats, hyperthyroid cats had lower VEMS (0.93 [0.84‐1.07] vs 1.27 [1.18‐1.39], P < .001) and FLEMS (1.24 [1.10‐1.35] vs 1.49 [1.39‐1.63], P < .001). After treatment, EMH increased (1.03 [0.89‐1.03] cm to 1.33 [1.17‐1.41] cm, P < .001), with abnormally low EMH normalizing in 36/41 (88%). Both VEMS (0.94 [0.87‐1.10] to 1.21 [1.10‐1.31], P < .001) and FLEMS (1.31 [1.17‐1.40] to 1.47 [1.38‐1.66], P < .001) also increased after treatment. Conclusions and Clinical Importance: Almost two‐thirds of hyperthyroid cats have abnormally low muscle mass when measured quantitatively by ultrasound. Successful treatment restores muscle mass in >85% of cats. EMH provided the best means of quantitating muscle mass in these cats.