ACTION OF ESTROGEN ON PLASMA CALCIUM AND ENDOSTEAL BONE FORMATION IN PARATHYROIDECTOMIZED PIGEONS

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Abstract
The 4 parathyroid glands of Carneau pigeons are entirely external and posterior to the thyroids. Apparently complete parathyroidectomy can be performed without injury to the thyroids. Parathyroidectomized birds were maintained for long-term tests either by dihydrotachysterol and Ca gluconate or by feeding 1 g. daily of Al(OH)3 (gelatinous). The first-named procedure increased the plasma Ca by about 2.0 mg.%, and the latter by double that amt. Daily doses of 0.25-0.5 mg. estradiol benzoate over 4-15 days increased the plasma Ca of 48 parathyroidectomized birds by 16.1 ([long dash]2.0 mg.) mg.%. Comparable treatment increased the plasma Ca of 36 normal pigeons by 16.3 mg.%. Estradiol benzoate was approx. as effective in promoting the formation of endosteal (medullary) bone in the femurs of parathyroidectomized pigeons as in normal pigeons. It was also effective in hypophysec-tomized immature pigeons. Adequate doses of estradiol benzoate promoted the formation of endosteal bone of [male] pigeons during all seasons of the year. In doses of 3 mg. daily for 15 days the androgen, androstenedione, gave macroscopic evidence of minimum endosteal bone formation in 2 tests and no effect in 2 tests. The effect, when present, probably resulted from the estrogenic potency of this androgen.