Congenital Erythropoietic Porphyria. II. The Effects of Induced Polycythemia

Polycythemia and anemia were inducedin a patient with congenital erythropoietic porphyria as a possible means ofaltering erythropoiesis and its attendantporphyrin production. Maintenance ofhematocrits at 50 per cent and 60 percent for periods of 2 weeks decreasedboth erythropoiesis and porphyrin excretion to about one-half of their initiallevels. Conversely with a hematocrit of25, erythropoiesis and porphyrin production were increased to about twice thebasal level. Examination of the marrowshowed fluorescence in all late normoblasts and indicated that the patient hasonly one red cell population. During induced polycythemia, a shift in marrowerythroid population to relatively matureforms, apparently related to delayedenucleation, was accompanied by a retention of the reticulocyte pool andfluorescent cells within the marrow. During anemia, the occurrence of relativelymore immature erythroid cells was accompanied by a shift of the reticulocytepool and fluorescent cells into the circulating blood. During polycythemia, increases were observed in the relativenumber of nuclear vacuoles peculiar tothis disease, in the retention of radioironin the marrow and in the relative amountof stercobilin excretion. In anemia theseparameters decreased towards normal.

Submitted on June 30, 1969 Revised on March 16, 1970 Accepted on April 1, 1970     

REMISSION OF HYPOPARATHYROIDISM DURING LACTATION: EVIDENCE FOR A PHYSIOLOGICAL ROLE FOR PROLACTIN IN THE REGULATION OF VITAMIN D METABOLISM

We studied a young woman with surgical hypoparathyroidism who, on her usual maintenance dose of calcitriol, developed hypercalcaemia 9 d postpartum when lactation was established. Serum values of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) values were very high (127 pg/ml). The patient remained without exogenous calcitriol treatment for 40 d, during which time serum 1,25(OH)2D3 levels remained within the normal range and serum calcium fell with a half-time of 27 d. The requirements for calcitriol increased to antepartum levels when lactation had ceased. There was a close negative correlation between requirements for calcitriol and serum PRL values. After weaning, an episode of hypercalcaemia was induced by increasing the dose of calcitriol. On stopping calcitriol the serum 1,25(OH)2D3 fell to low values (4 pg/ml) within 2 d and serum calcium fell with a half-time of 3 d, necessitating the early reintroduction of calcitriol. We conclude that in hypoparathyroidism exogenous vitamin D requirements fall during lactation because of enhanced endogenous production of 1,25(OH)2D3. The lactation-associated increase in circulating 1,25(OH)2D3 concentrations thus results from a parathyroid hormone-independent mechanism, possibly by an effect of PRL on the 1 alpha-hydroxylase.