title: Effect of age on the response to parathyroid hormone.
abstract: Serum phosphate (PO4) levels and the tubular threshold for PO4 corrected for glomerular filtration (TP/GF) are age-dependent, being higher in children than in adults. We evaluated the effect of age on the response to infusion of parathyroid hormone(1-34) (PTH) in healthy children (n = 8) and adults (n = 12). In addition, six patients with pseudohypoparathyroidism (PHP) and two with PTH deficiency (hypoparathyroidism [HP]) were also studied. At baseline, TP/GF in normal subjects was inversely correlated with urinary cyclic adenosine monophosphate corrected for glomerular filtration (UcAMP/GF) (P < .0359). After PTH administration in the controls, UcAMP/GF was inversely correlated with TP/GF (P < .0007) and directly correlated with maximal fractional extraction of PO4 (FEP) (P < .0002). The slope of the regression of TP/GF (P < .0076) and FEP (P < .0034) with UcAMP/GF was steeper in children than in adults. Two HP patients had high PTH-stimulated UcAMP/GF levels, but stimulated TP/GF and FEP were not changed commensurate with levels that would expected from the normative data. In six patients with PHP, PTH-stimulated TP/GF was also correlated with peak UcAMP/GF (r = .96, P < .002). PHP patients could be distinguished from normal controls based on the combination of low peak FEP or high TP/GF together with low peak UcAMP/GF. Thus, in normal subjects, the phosphaturic response to PTH is correlated with the increase in urinary cAMP and is age-dependent, with a greater decrease of TP/GF in children than in adults.
authors.affiliation: Department of Pediatrics, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: A
authors.initials: A
authors.lastname: Zung
authors.forename: S A
authors.initials: SA
authors.lastname: Chalew
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000097:blood / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D000242:Cyclic AMP / Q000378:metabolism / Q000652:urine*; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007011:Hypoparathyroidism / Q000378:metabolism; D007262:Infusions, Intravenous; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010710:Phosphates / Q000097:blood / Q000378:metabolism*; D011547:Pseudohypoparathyroidism / Q000378:metabolism; D012016:Reference Values; D019379:Teriparatide / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D010710:Phosphates; D019379:Teriparatide; D000242:Cyclic AMP