Plasma hydroxyproline peptide

Vitamin C status is generally assessed by estimating the saturation of body reserves or measuring plasma and leukocyte concentrations of the vitamin. Urinary excretion of hydroxyproline-containing peptides is reduced in people with inadequate vitamin C status, but a number of other factors that affect bone and connective tissue turnover confound interpretation of the results (Bates, 1977). The ratio of deoxypyridinolineipyridinoline compounds derived from collagen cross-links provides a more useful index, but is potentially affected by copper status (Tsuchiya and Bates, 1997). 

Marked elevations of plasma peptide hydroxyproline have been observed by Dubovsky et al. in chronic renal failure (D7). The highest levels were seen when uremia and severe bone disease occurred together. Removal of the parathyroids in four patients (three primary and one secondary hyperparathyroidism) was associated with return to normal levels when renal function was normal, and significant reduction when renal failure was present. It seems possible that plasma peptide hydroxyproline might be a rapidly changing and sensitive indicator of bone metabolism which could be studied even with renal impairment, a major obstacle to most current techniques in the diagnosis of hyperparathyroid states. 

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