Secretion of parathyroid hormone after surgical trauma

Serum intact-parathyroid hormone level following total knee arthroplasty

PURPOSE

To evaluate short-term parathyroid hormone (PTH) secretion following total knee arthroplasty (TKA).

METHODS

119 Caucasian postmenopausal women aged 49 to 81 (mean, 69.8) years who underwent TKA for end-stage knee osteoarthritis were included. Serum levels of intact-PTH, calcium, phosphorus, and creatinine were evaluated pre- and post-operatively (on days -1 and 7). Creatinine clearance was also calculated.

RESULTS

In 67 of the patients, serum intact-PTH levels decreased after TKA; this sample proportion was not significant (p=0.82). In 16 of the patients, such levels elevated abnormally (above normal range). In the remaining 36 patients, such levels elevated within the normal range. Therefore, the mean serum intact- PTH level of all patients increased slightly after TKA (45.4 vs. 45.3, p=0.162). The serum intact-PTH level did not correlate to body weight (r=-0.045, p=0.624), patient age (r=-0.061, p=0.508), serum creatinine level (r=0.084, p=0.366), and clearance of creatinine (r=-0.037, p=0.692).

CONCLUSION

In most postmenopausal women, the serum intact-PTH level decreased moderately following TKA, but in some, the level was abnormally elevated. This may interfere the prosthesis incorporation process.

Effects of prolonged adrenaline infusion and of mental stress on plasma minerals and parathyroid hormone

The role of the sympatho-adrenal system for the secretion of PTH in humans is not established. Previous studies on the effects of adrenaline on plasma mineral homeostasis have focused on injections or short-term infusions of adrenaline, and conflicting results concerning calcium and parathyroid hormone (PTH) responses have been reported. We therefore infused adrenaline or placebo continuously for 3 h to 10 healthy volunteers and studied several plasma minerals, as well as PTH levels. Venous plasma adrenaline concentrations increased to the upper physiological range (5 nmol l-1) during adrenaline infusion. Another nine volunteers were exposed for 25 min to mental stress (a colour word conflict test; CWT), which causes marked circulatory changes and raises plasma catecholamine concentrations. Plasma ionized and total calcium, and magnesium concentrations were slowly and gradually reduced during infusion of adrenaline, but there was only a small increase in PTH. Plasma potassium was decreased by adrenaline within 30 min and thereafter did not change further during infusion. There was a marked but transient increase in the plasma free fatty acids concentration, which were not related to the reduction of the calcium or magnesium levels. The adrenaline-induced decrements in calcium, magnesium and potassium, and increases in heart rates persisted 30 min after the infusion, despite a rapid decrease in plasma adrenaline concentrations within 5 min of termination of the infusion. Plasma phosphate concentrations were lowered during the first 90 min of adrenaline infusion, but after 3 h they had returned to baseline despite continued infusion. CWT induced small increments of the plasma ionized calcium and PTH concentrations. Plasma potassium levels were raised despite increases in plasma adrenaline at the beginning of the stress test, while phosphate values were reduced at the end of the test. Thus, long-lasting elevations of circulating adrenaline lower plasma ionized and total calcium, phosphate, magnesium and potassium, but the time courses for these changes differed markedly. Despite the reduction of plasma ionized calcium there was only little increase in PTH and thus no indication that sustained elevations of circulating adrenaline stimulates the secretion of PTH in vivo in humans. Responses to acute mental stress and adrenaline infusion differed qualitatively, indicating that adrenaline responses to stress are of minor importance in this respect.