ROLE OF THYROID HORMONE IN THE PATHOGENESIS OF JOINT DISEASE IN MICE

Effects of Radiothyroidectomy and High-Fat Diets

¹ Snodgras Laboratory, Hospital Division, City of St. Louis, and the Department of Pathology, Washington University, School of Medicine, St. Louis

In mice of various strains the structure and function of the thyroid gland vary, mice of strain Dba having comparatively active glands and mice of strain C₅₇BL possessing comparatively inactive thyroid glands. In C₅₇BL males, a high-fat diet increased the incidence and advanced the onset of degenerative joint disease, while in Dba males, the fat-enriched diet failed to exert significant effects on the articular structures. It was assumed that differences in thyroid activity might be related to the strains differences in the response to the high-fat diet. The fat-enriched ration was, therefore, fed to adult mice of both strains, after their thyroid glands had been destroyed by injection of I¹³¹. Following this treatment, the response of the mice of the two strains was reversed. In the absence of thyroid secretions, C₅₇BL mice became less susceptible than Dba mice, while Dba mice became more susceptible to the injurious effect of the high-fat diet than Dba mice with intact thyroid glands.

Radiothyroidectomy also produced characteristic articular chansges, which were different from degenerative joint disease and which were designated "athyroid joint disease". The susceptibility to this lesion likewise varied with the thyroid activity characteristic of the strain. Dba mice showed a high incidence and a severe degree of this disease, while C₅₇BL mice were less frequently affected and showed only low-grade lesions. A fat-enriched diet, in turn, adversely influenced the course of athyroid joint disease in both strains of mice.

Thus the thyroid hormone plays a major role in the development of the growing joint and in the maintenance of the adult articular structures under normal conditions, as well as under abnormal conditions. The extent of this influence varies with the degree of thyroid function characteristic of the particular strain of mice or of the individual.

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