Abstract
Rat parathyroids were studied both after nephrectomy and after combined nephrectomy and adrenalectomy. As early as 24 hr. after nephrectomy there were morphological indications of increased parathyroid activity in the form of increased glandular volume and enlarged cell nuclei. The corresponding changes after combined nephrectomy and adrenalectomy were less marked and the total serum Ca was higher than after nephrectomy only. These observations suggest that the adrenals could induce a change in Ca homeostasis opposite to that of the parathyroids.