Normal pattern of parathyroid response to blood calcium lowering in primary hyperparathyroidism: a citrate clamp study

Schwarz, Peter; Serensen, H. A.; Momsen, Günther; McNair, Peter; Transbel, I.

doi:10.1111/j.1365-2265.1992.tb02336.x

Cited by 15 publications

(6 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The citrate clamp technique allowed a carefully monitored reduction in whole‐blood ionised calcium to concentrations within acceptable limits of safety. Changes in serum PTH in our healthy controls were consistent with other studies [ 2, 6, 7 12, 16,]. There was an initial peak an average of seven times above baseline, followed by a slower fall to a mean steady‐state level at twice the basal concentration.…”

Section: Discussionsupporting

confidence: 91%

See 1 more Smart Citation

Dynamic assessment of parathyroid function in acute malaria

Davis

Choo²,

Ibrahim

et al. 1998

Journal of Internal Medicine

View full text Add to dashboard Cite

Objectives. To investigate the dynamic parathyroid response to rapidly induced, sustained hypocalcaemia in patients with acute malaria and in healthy volunteers. Design. Serum intact parathormone (PTH) concentrations were measured on samples taken before and during a variable-rate tri-sodium citrate infusion designed to 'clamp' the whole blood ionised calcium concentration 0.20 mmol L Ϫ1 below baseline for 120 min. Subjects. Six Malaysian patients aged 17-42 years with acute malaria, four of whom were restudied in convalescence, and 12 healthy controls aged 19-36 years. Main outcome measures. Whole-blood ionised calcium and serum intact PTH concentrations. Results. The mean (SD baseline ionised calcium was lower in the malaria patients than in controls (1.09 Ϯ 0.06 vs. 1.18 Ϯ 0.03 mmol L Ϫ1 , respectively; P ϭ 0.01) but PTH concentrations were similar (3.0 Ϯ 1.8 vs. 3.3 Ϯ 1.3 pmol L Ϫ1 ; P ϭ 0.33). Target wholeblood ionised calcium concentrations were achieved more rapidly in the controls than the patients (within 15 vs. 30 min) despite significantly more citrate being required in the patients (area under the citrate infusion-time curve 0.95 (0.25 vs. 0.57 Ϯ 0.09 mmol kg Ϫ1; P Ͻ 0.01). The ratio of the change in serum PTH to that in ionised calcium (⌬PTH/⌬Ca 2ϩ ), calculated to adjust for differences in initial rate of fall of ionised calcium, was similar during the first 5 min of the clamp (132 Ϯ 75 ϫ 10 Ϫ6 vs. 131 Ϯ 43 ϫ 10 Ϫ6 in patients and controls, respectively, P Ͼ 0.05), as were steady-state serum PTH levels during the second hour (7.0 Ϯ 2.2 pmol L Ϫ1 in each case). Convalescent patients had normal basal ionised calcium levels but the lowest serum intact PTH levels before and during the clamp, consistent with an increase in skeletal PTH sensitivity after treatment. Conclusions. There is a decreased ionised calcium 'set point' for basal PTH secretion but a normal PTH response to acute hypocalcaemia in malaria. Skeletal resistance may attenuate the effects of the PTH response but patients with malaria appear relatively resistant to the calcium chelating effects of citrated blood products.

show abstract

Section: Discussionsupporting

confidence: 91%

“…During dialysis, the serum calcium returns to normal and serum intact PTH concentrations fall to levels within the reference range [ 5]. These data provide evidence that, consistent with other conditions associated with an altered set point [ 6, 7], a degree of parathyroid gland responsiveness is maintained.…”

Section: Introductionmentioning

confidence: 55%

Dynamic assessment of parathyroid function in acute malaria

Davis

Choo²,

Ibrahim

et al. 1998

Journal of Internal Medicine

View full text Add to dashboard Cite

show abstract

“…Numerous studies have demonstrated reciprocal changes in S-PTH in response to changes in serum calcium [ 10-171. Recently, carefully controlled citrate clamp and calcium clamp studies have demonstrated a striking similarity respecting parathyroid responsiveness in patients with PHPT and normal humans. In both groups lowering of B-Ca2+ released a large burst of preformed PTH(1-84) from the intracellular depots followed by a sustained hypersecretion of PTH( 1-84) [6,18], while raising of B-Ca2+ readily suppressed PTH( 1-84) secretion All observations from previous dynamic studies support the current calcium set-point hypothesis according to which abnormal parathyroid glands are 'set' to maintain B-Ca2+ at a constant, but higher, level than normal parathyroid glands are [9,20,2 11.…”

Section: Introductionmentioning

confidence: 99%

Inter‐relations between the calcium set‐points of Parfitt and Brown in primary hyperparathyroidism: a sequential citrate and calcium clamp study

Schwarz¹,

Sørensen²,

Transbøl³

1994

Eur J Clin Investigation

Self Cite

View full text Add to dashboard Cite

The objective of the present study was to compare the calcium set-points of E. M. Brown and A. M. Parfitt obtained by sequential citrate and calcium clamp in patients with primary hyperparathyroidism and healthy controls. Twenty-six patients with primary hyperparathyroidism were investigated and compared to 22 healthy volunteers. All participants were investigated by sequential calcium lowering and raising comprising the following four phases: Phase (1) blood ionized calcium lowering of about 0.20 mmol l-1; phase (2) steady-state (relative) hypocalcaemia of blood ionized calcium 0.20 mmol l-1 below baseline; phase (3) blood ionized calcium is raised to about 0.20 mmol l-1 above baseline; and phase (4) (relative) hypercalcaemia of blood ionized calcium 0.20 mmol l-1 above baseline. Serum parathyroid hormone (1-84) was measured by an immunoradiometric assay. Blood ionized calcium was measured by a calcium selective electrode. We found the calcium set-points of Parfitt to be 1.42 mmol l-1 (SD 0.12, n = 52) vs. 1.25 mmol l-1 (SD 0.04, n = 44) in patients and controls, respectively (P < 0.001). The calcium set-points of Brown were 1.32 mmol l-1 (SD 0.10, n = 26) vs. 1.13 mmol l-1 (SD 0.04, n = 22), respectively (P < 0.001). By comparing the calcium set-points of Parfitt and Brown, a strikingly good correlation was observed, in patients (r = 0.91, P < 0.001) and in controls (r = 0.85, P < 0.001). We demonstrate in this paper in vivo that Brown's and Parfitt's calcium set-points are raised in primary hyperparathyroidism and return to normal following parathyroidectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

“…In addition, more frequent electrocardiographic assessment would better characterise relations such as that found in the present study, the protocol for which was based on previous recommendations. '8 19 Our findings relate to healthy volunteers studied under controlled conditions using a technique which lowers the whole blood ionised calcium concentration without affecting the concentrations of other electrolytes, including potassium and magnesium, which may influence the QT interval.7 In clinical situations in which the ionised calcium concentration is lowered promptly, such as during rapid transfusion of citrated blood products,22 increased sympathetic tone, simultaneous changes in serum potassium, and even administration of drugs known to affect ventricular repolarisation may invalidate the use of electrocardiographic monitoring as a guide to a safe transfusion rate and the need for intravenous calcium replacement. Nevertheless, further studies of a possible hysteresis relation would be of interest and importance in such patients.…”

Section: Discussionmentioning

confidence: 99%