Parathyroid hormone-related protein (PTHrP) does not regulate 1,25-dihydroxyvitamin D serum levels in hypercalcemia of malignancy.
We investigated in humoral hypercalcemia of malignancy whether parathyroid hormone-related protein (PTHrP) elevation causes a rise in 1,25-dihydroxyvitamin D (1,25-(OH)2 D) serum levels. We assessed 41 patients with hypercalcemia of malignancy in a prospective study. There were 19 patients who had serum PTHrP levels in the normal range; 22 patients had elevated serum PTHrP levels. All patients were treated with the bisphosphonate pamidronate resulting in a drop of serum calcium (p < 0.0001) and serum phosphate (p < 0.0023) within 12 days, independent of the group. Parathyroid hormone (PTH) was suppressed at the start of therapy and rose to within the normal range during therapy (p < 0.0001), regardless of the PTHrP levels. PTHrP levels were not influenced by calcium lowering therapy. The serum levels of 1,25-(OH)2 D were either suppressed or in the low normal range at the beginning of the study, without any significant difference between both groups. All patients showed a rise in 1,25-(OH)2 D during bisphosphonate therapy (p < 0.0001), independent of their PTHrP levels. Thus PTHrP did not influence the calcium, phosphate-, or PTH-dependent regulation of 1,25-(OH)2 D during calcium lowering therapy. We conclude, that PTHrP does not stimulate renal 1-hydroxylase activity in humoral hypercalcemia of malignancy.
Schilling
T
T
Department of Internal Medicine I, Endocrinology and Metabolism, University of Heidelberg, Germany.
Pecherstorfer
M
M
Blind
E
E
Leidig
G
G
Ziegler
R
R
Raue
F
F
D000328:Adult; D000368:Aged; D004100:Dihydroxycholecalciferols / Q000097:blood*; D004164:Diphosphonates / Q000627:therapeutic use; D005260:Female; D006801:Humans; D006934:Hypercalcemia / Q000097:blood* / Q000188:drug therapy / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D000077268:Pamidronate; D010281:Parathyroid Hormone / Q000502:physiology; D044162:Parathyroid Hormone-Related Protein; D011446:Prospective Studies; D011506:Proteins / Q000502:physiology*
D004100:Dihydroxycholecalciferols; D004164:Diphosphonates; C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D000077268:Pamidronate