Background Abnormalities in calcium phosphate (Ca-P) metabolism and Ca-P related hormones are well documented in patients with essential hypertension (EH), but less in patients with non insulin dependent diabetes mellitus (NIDDM). The present study was designed to assess the influence of antihypertensive treatment on the responsiveness of PTH secretion to an oral phosphate load (100 mmol) in EH and hypertensive NIDDM patients (CINNT).
Material and methods In 29 patients with EH (45.6 ± ± 1.3 y) - NTS, and 32 CINNT (48.4 ± 0.9 y) plasma intact PTH (iPTH) was assessed before and after 3 weeks of treatment. 14 NTS and 16 CINNT patients were treated with nifedipine (N), while 15 NTS and 16 CINNT with enalapril (E). iPTH and 25-OH-D in plasma were estimated before (0) and iPTH 4, 8, 12, 18 and 24 hours after an oral phosphate load. Urinary excretion of calcium and phosphate were also estimated one day before [U-Ca (B) and U-P (B)] and at the day of an oral P load [U-Ca (A) U-P (A)]. A control group of 13 healthy subjects (GK) (46.2 ± 1.9 y) was also examined.
Results NTS patients showed lower 25-OH-D plasma levels than GK and CINNT (22.9 ± 2.7 vs. 33.7 ± 5.6 p = 0.02 and 28.7 ± 2.7 p = 0.04 ng/ml respectively). Before treatment NTS and CINNT patients showed an exaggerated response of PTH secretion to a phosphate load (as expressed as the AUC) than GK [757 ± 52 vs. 790 ± 54 vs. 607 ± 59 (pg/ml)*24h respectively] and a higher calciuria [2.48 ± 0.2 vs. 2.42 ± 0.2 vs. 1.77 ± 0.2 mmol/d]. After N treatment a nonsignificant increase of the response of PTH secretion to P load was noticed in both groups of patients. In contrast E treatment was accompanied by a significantly suppressed response of PTH secretion to P load [755 ± 78 vs. 602 ± 64 (pg/ml)*24h in NTS] and [844 ± 87 vs. 631 ± 66 (pg/ml)*24h in CINNT] in both examined group.
Conclusion From results obtained in this study E but not N seems to exert a suppressive effect on PTH secretion both in NTS and NIDDM patients.