We performed graded calcium infusions twice in six normal young men, once without medication and a second time after they had received therapeutic doses of lithium carbonate for 5 days/The serum lithium level was 0.73 ± 0.08 meq/ liter (mean ± SE) at the beginning of the calcium infusion and reached 0.97 ± 0.13 150 min after receiving a lithium dose (210 min after beginning the test). There was no significant difference in mean basal serum calcium, plasma PTH, or nephrogenous cAMP for the untreated and treated periods. There was also no significant difference in calcium suppressibility of PTH secretion, as reflected by changes in nephrogenous cAMP. Changes i n plasma PTH in response to calcium infusion likewise did not differ for the two periods, with the exception of a slightly greater degree of suppression in the unmedicated state (77% vs. 57% on lithium: P < 0.02, by paired t test) at the last time point of the calcium infusion. The data show that short term administration of therapeutic doses of lithium does not alter the set-point for calcium suppression of PTH secretion in man. Further studies of calcium suppressibility of PTH secretion in subjects receiving long term lithium therapy will be needed to evaluate the patho-physiology of lithium-induced hypercalcemia.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical