The article presents the results of studies of occupational fluorosis pathogenesis on experimental model of chronic fluoride intoxication (CFI). In early fluoride intoxication, fluoride and calcium in the body are in compensatory relations. Later, they are disturbed. High reaction ability of fluoride in CFI is associated with hypocalciemia which triggers parathyroid hyperactivity. This results in hyperproduction of PHH which is unrelated with development of secondary hyperparathyrosis. CFI is accompanied also with elevated calcitonin having a hypocalciemic and hypophosphatemic action. The experiments showed double content of collagen fragments of bone tissue in urine of animals with fluoride intoxication which reflects resorption of bone tissue. Serum osteocalcin rose three-fold as it was unable to include in the bone tissue. There was also activation of lipid peroxidation in subnormal activity of respiratory enzymes.