Biomedical subjects
H T McPherson
Publications and source records attributed to H T McPherson.
1,25-Dihydroxycholecalciferol deficiency: the probable cause of hypocalcemia and metabolic bone disease in pseudohypoparathyroidism.
Pseudohypoparathyroidism (PsH) is a genetic disease characterized by hypocalcemia, hyperphosphatemia, and metabolic unresponsiveness to parathyroid hormone (PTH). The administration of PTH elicits neither a significant rise in serum calcium (calcemic response) nor a decrease in the renal tubule reabsorption of phosphorus (phosphaturic response). The diminished phosphaturic response is due to an inability of PTH to generate cyclic AMP in renal tubule cells. We investigated the question of whether hypocalcemia and deficient calcemic response to PTH are due to a similar cyclic AMP defect in bone or to an acquired vitamin D deficiency. Four patients were studied. The active form of vitamin D (1,25-dihydroxycholecalciferol) was measured in 3 and was low. Treatment with vitamin D2 restored the serum calcium and the calcemic response to PTH to normal without changing the impaired renal response. Bone biopsy was performed in 2 patients and showed morphologic evidence of increased osteoclastic activity and osteomalacia. The data indicate that the hypocalcemia and bone disease in PsH are due to active vitamin D deficiency, possibly resulting from the genetic renal lesion.
The early diagnosis of medullary carcinoma of the thyroid gland in patients with multiple endocrine neoplasia type II.
Pentagastrin is a potent stimulator of thyrocalcitonin secretion from "C" cells. Since medulllary carcinoma of the thyroid gland (MCT) is a tumor composed of "C" cells, pentagastrin was used to screen a large kindred with multiple endocrine neoplasia type II (MCT, pheochromocytoma (s), and parathyroid hyperplasia). Four children with no thyroid abnormalities evident on physical examination, with negative thyroid scans, and with normal levels of plasma thyrocalcitonin both before and after calcium infusion, were found to have elevated peripheral levels of this hormone following pentagastrin injection. All four children were found to have very small foci of MCT, in both thyroid lobes at the time of total thyroidectomy. Pentagastrin stimulation used conjointly with selective catheterization of the inferior thyroid vein provided even greater diagnostic accuracy in detecting elevations in thyrocalcitonin secretion. This test has great diagnostic utility, especially in screening patients with multiple endocrine neoplasia type II.