title: Parathyroid responsiveness to hypocalcemic and hypercalcemic stimuli in adult growth hormone deficiency after growth hormone replacement.
abstract: Adult growth hormone deficiency (AGHD) is associated with osteoporosis. Previous reports have suggested that alterations in parathyroid gland responsiveness to changes in calcium concentration may play a role in the genesis of osteoporosis in untreated AGHD patients. We investigated the endogenous parathyroid hormone [PTH-(1-84)] response to hypocalcemic and hypercalcemic stimuli induced by sodium EDTA and calcium gluconate infusion, respectively, and to PTH-(1-34) infusion in AGHD patients before and during GH replacement (GHR). We have demonstrated that the maximum PTH-(1-84) stimulation and suppression occurred at significantly higher calcium concentrations and in response to smaller changes in calcium concentrations after GHR. The calcemic response to the effects of PTH-(1-34) infusion significantly increased after GHR. The calcium set point (the calcium concentration at which the rate of PTH secretion is one-half of its maximal value) significantly increased in all groups after 3 mo on GHR, and it increased further at 12 mo. Our results suggest increased parathyroid gland sensitivity to smaller changes in serum calcium and increased end-organ sensitivity to the effects of PTH in AGHD patients after GHR. These findings may help us to understand the mechanisms underlying the genesis of osteoporosis in AGHD patients.
authors.affiliation: Department of Diabetes & Endocrinology, Royal Liverpool University Hospital, Liverpool L7 8XP, UK. DRAAHMAD@Yahoo.com
authors.forename: Aftab M
authors.initials: AM
authors.lastname: Ahmad
authors.forename: Marion T
authors.initials: MT
authors.lastname: Hopkins
authors.forename: Joegi
authors.initials: J
authors.lastname: Thomas
authors.forename: Brian H
authors.initials: BH
authors.lastname: Durham
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
authors.forename: Jiten P
authors.initials: JP
authors.lastname: Vora
mesh_terms: D000328:Adult; D000368:Aged; D002125:Calcium Gluconate; D002614:Chelating Agents; D004492:Edetic Acid; D019382:Human Growth Hormone / Q000008:administration & dosage* / Q000172:deficiency*; D006801:Humans; D006934:Hypercalcemia / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism*; D006996:Hypocalcemia / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008875:Middle Aged; D010280:Parathyroid Glands / Q000187:drug effects* / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000008:administration & dosage; D010446:Peptide Fragments / Q000008:administration & dosage; D044169:Receptors, Calcium-Sensing / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D044169:Receptors, Calcium-Sensing; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D004492:Edetic Acid; D002125:Calcium Gluconate