Excess parathyroid hormone adversely affects lipid metabolism in chronic renal failure

Hyperlipidemia is common in chronic renal failure (CRF), but the underlying mechanisms are not clearly defined. Certain data points toward a potential role for the state of secondary hyperparathyroidism of CRF in its pathogenesis. We examined the effects of parathyroid hormone (PTH) on lipid metabolism utilizing intravenous fat tolerance test (IVFTT) and post-heparin lipolytic activity in five normal dogs, in six animals with CRF and secondary hyperparathyroidism (NPX) and in six normocalcemic-thyroparathyroidectomized dogs (NPX-PTX) with comparable degree and duration of CRF. NPX dogs had fasting hypertriglyceridemia (82 + 6.0 mg/dl vs. 49 +/- 2.7 mg/dl in normal dogs, P less than 0.01), abnormal IVFTT, and reduced post-heparin plasma LPL activity (151 +/- 10 vs. 275 +/- 15 mumol fatty acids/ml/min in normal dogs, P less than 0.01). The NPX-PTX dogs had normal fasting levels of serum triglycerides (42 +/- 0.6 mg/dl), normal IVFTT, and normal post-heparin plasma LPL (317 +/- 19 mumol fatty acids/ml/min) despite CRF. Post-heparin HL activity in plasma was not different between NPX and NPX-TPX dogs. The results show that excess blood levels of PTH and not other consequences of CRF are mainly responsible for the abnormalities in lipid metabolism. The data are consistent with the notion that excess PTH reduces post-heparin LPL activity in plasma, which in turn results in impaired lipid removal from the circulation and consequently hyperlipidemia.