Endocrine Abstracts

Introduction: Major factor that modulates the PTH secretion is serum Ca level. Paratyhyroid gland also receives direct autonomic innervation. To date, measurement of several hormones such as cortisol,prolactin, renin and aldosteron were found to be affected by changing the posture from recumbent to the upright position. In the present study, we aimed to investigate postural change of PTH in normal individuals and patients with primary hyperparathyroidism (PHPT).

Methods and results: 23 patients with PHPT and nine healthy controls were enrolled. Blood samples were taken from all indivuduals after 12 h of fasting. Following replacement of an i.v. catheter, the patients were requested to rest in bed in recumbent position but not sleeping for an hour and blood samples were obtained for PTH and Ca measurements at the 45th and 60th min of resting. Afterwards, the patients changed the posture to the upright position and stood up for an hour and again blood samples were obtained at the 45th and 60th min of standing. Pulses and blood pressures of all individuals were recorded in both postures. In the group of patients with PHPT, mean serum PTH was measured as 75.36 pg/ml higher during upright position compared to recumbent position and the difference was statistically significant. Mean serum Ca was also significantly higher in upright position. In the control group mean serum PTH was measured only 3.09 pg/ml higher during the upright postion compared to recumbent position and the difference didn’t reach statistical significance. However mean serum Ca level was 0.46 mg/dl higher during the upright postion compared to the recumbent which resulted in a statistically significant difference.

Conclusion: It was reported that total calcium measurement increases in upright posture which should normally decrease the measured PTH level. However PTH secretion is autonomic in PHPT and increased in upright position regardless of serum Ca level.