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Veterinary Clinical Research


As pets age, quality of life and mobility can be impacted by pain of osteoarthritis and age-related muscle atrophy (sarcopenia). The purpose of this randomized, double-blinded, placebo controlled study was to evaluate the effects of Fortetropin®, a nonthermal-pasteurized, freeze-dried, fertilized egg yolk product, on mobility in senior dogs. Mobility scores were calculated using a standardized and validated client-based survey, the Liverpool Osteoarthritis in Dogs (LOAD) questionnaire. Results showed mild, but statistically significant, improvement of the mobility scores for the treatment group at both week 6 (p= 0.03) and week 12 (p= 0.006) compared to the baseline score. No statistical improvement was noted at any time point in the placebo group or between the treatment and placebo group.


Hetrick, Katie, Kenneth R. Harkin, and James K. Roush. “Evaluation of Fortetropin in geriatric and senior dogs with reduced mobility.” The Canadian Veterinary Journal= La Revue Veterinaire Canadienne 63.10 (2022): 1057-1060. 

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Objective: To determine if a commercial myostatin reducer (Fortetropin®) would inhibit disuse muscle atrophy in dogs after a tibial plateau leveling osteotomy.

Design: A prospective randomized, double-blinded, placebo-controlled clinical trial.

Animals: One hundred client-owned dogs presenting for surgical correction of cranial cruciate ligament rupture by tibial plateau leveling osteotomy.

Procedures: Patients were randomly assigned into the Fortetropin® or placebo group and clients were instructed to add the assigned supplement to the dog’s normal diet once daily for twelve weeks. Enrolled patients had ultrasound measurements of muscle thickness, tape measure measurements of thigh circumference, serum myostatin level assays, and static stance analysis evaluated at weeks 0, 8, and 12.

Results: From week 0 to week 8, there was no change for thigh circumference in the Fortetropin® group for the affected limb (-0.54cm, P = 0.31), but a significant decrease in thigh circumference for the placebo group (-1.21cm, P = 0.03). There was no significant change in serum myostatin levels of dogs in the Fortetropin® group at any time point (P>0.05), while there was a significant rise of serum myostatin levels of dogs in placebo group during the period of forced exercise restriction (week 0 to week 8; +2,892 pg/ml, P = 0.02). The percent of body weight supported by the affected limb increased in dogs treated with Fortetropin® (+7.0%, P<0.01) and the placebo group (+4.9%, P<0.01) at the end of the period of forced exercise restriction. The difference in weight bearing between the Fortetropin® and placebo groups was not statistically significant (P = 0.10).

Conclusion: Dogs receiving Fortetropin® had a similar increase in stance force on the affected limb, no significant increase in serum myostatin levels, and no significant reduction in thigh circumference at the end of the period of forced exercise restriction compared to the placebo. These findings support the feeding of Fortetropin® to prevent disuse muscle atrophy in canine patients undergoing a tibial plateau leveling osteotomy.


White, Dana A., et al. “Fortetropin inhibits disuse muscle atrophy in dogs after tibial plateau leveling osteotomy.” PLOS ONE 15.4 (2020): e0231306.

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Objective: To evaluate the effect of a single administration of 6 and 12 g of Fortetropin compared to placebo on serum myostatin in healthy, adult dogs over a 72-h period.

Methods: Prospective, placebo-controlled, randomized, double-blind, crossover study. Ten hospital-employee-owned healthy adult dogs aged 2 to 8 years old were enrolled in the study. Blood samples were collected prior to and then 12-, 24-, 36-, 48-, and 72-h following administration of the test agent (6 and 12 g) or placebo. Serum samples were processed according to manufacturer’s guidelines for canine serum using GDF-8/Myostatin Quantikine ELISA kit (R&D Systems). Analysis-of-variance (ANOVA) analyses were carried out where P < 0.05 was deemed significant.

Results: Mean serum myostatin was not significantly lower in treatment groups of either low or high dose compared to placebo at any time point. Baseline mean serum myostatin in low and high dose treatment groups was 29,481 (SD = 5,224) and 32,214 pg/mL (SD = 7,353), respectively. Placebo group low and high dose baseline mean serum myostatin was 30,247 (SD = 5,875) and 28,512 (SD = 5,028).

Conclusion: The results of this study indicate that administration of single 6 or 12 g dose of Fortetropin does not reduce serum myostatin in healthy adult dogs over a 72-h period.

Clinical Importance: Oral supplements, like Fortetropin, require further studies to determine the efficacy and bioavailability in order to guide clinical use in dogs.

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MYOS CORP is an emerging company focused on improving muscle health through the development of advanced nutrition products.

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Morris Technical Center
45 Horsehill Road, Suite 106
Cedar Knolls, NJ 07927

(973) 509-0444



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