The Parathyroid Glands and Calcium Deficiency in the Rat

SUMMARY In rats maintained on a diet deficient in calcium but otherwise adequate, there is increased parathyroid activity. Evidence is presented which shows that the osteoporosis of calcium deficiency is the result of this activity. The rapid bone turnover which characterizes this form of osteoporosis is dependent on the presence of the parathyroid glands, and in their absence it is not seen, but instead bone turnover is much slower than normal. Hypoparathyroidism protects the skeleton from the osteoporosis due to calcium deficiency, but at the expense of somatic and skeletal growth.