Parathyroid hormone changes during phosphorus load in patients with chronic renal insufficiency with low serum parathyroid hormone or adynamic bone disease

Adynamic bone disease (ABD) is frequently associated with low serum parathyroid hormone (PTH) concentrations. Many clinical and therapeutic conditions have been associated with ABD, and recently, a low phosphorus intake accompanied by low serum concentration of phosphorus and PTH has been described.

AIM

To evaluate the parathyroid gland response of chronic renal insufficiency patients (CRI) with low serum PTH or ABD to a phosphorus load.

METHODS

We examined the effects of 0.5 and 1.0 g/d of phosphorus load over a period of 60 days in 18 patients with mild CRI with a bone biopsy showing ABD (n = 7) or with low serum PTH (serum intact PTH < or = 40 ng/l) and serum phosphorus < 4.5 mg/dl (n = 11).

RESULTS

Serum intact PTH increased significantly only after 1 g of phosphorus (58.5 to 83 ng/l) with a median percent increase of 72%. PTH secretion increased more in patients with lower basal PTH levels (81%). Serum phosphorus did not change significantly and urinary phosphorus increased from 487 to 1,062 mg/dl (p < 0.05). Significant decreases in serum ionized calcium (from 1.26 to 1.19 mmol/l) and calcitriol (from 34.5 to 24.9 pg/ml) were observed. Changes in PTH were inversely correlated with changes in serum ionized calcium (r = -0.54, p < 0.05) and the final PTH concentrations were positively correlated with changes in serum phosphorus (r= 0.52, p < 0.05).

CONCLUSIONS

The parathyroid glands of chronic renal insufficiency patients with "relative hypoparathyroidism" or ABD responded to a phosphorus load with an increase in serum PTH levels. The decrease in serum ionized calcium and calcitriol as well as minimal changes in serum phosphorus appeared to be involved in this response.

Reversal of left ventricular hypertrophy with isradipine induces diminution of cardiac arrhythmias

The left ventricular hypertrophy (LVH) of hypertension is often associated with ventricular arrhythmias, which may increase the risk of cardiovascular mortality. Our study was therefore designed to assess whether pharmacological reversal of LVH was associated with the diminution of LV ectopic beats. The antihypertensive agent selected for the study was the dihydropyridine calcium antagonist isradipine (2.5 to 5.0 mg/day orally), which induces rapid regression of LVH. A marked temporal association was observed between regression of LV mass and reductions in the total number of ventricular extrasystoles and in paired beats. Furthermore, there was a diminution of the complexity of the form of ventricular ectopic beats during antihypertensive treatment. No changes in serum electrolytes were documented to account for this control of cardiac arrhythmias. We conclude that the reversal of LVH obtained with isradipine is accompanied by control of the ventricular arrhythmias in hypertensive patients. It is possible that this cardioprotective action may be associated non-specifically with the reduction in LV mass, although a drug- or class-specific action cannot be ruled out.