PTH and Huntington disease: The aims of the present study were to investigate whether there are any differences in the distribution of circulating PTH fragments in PD vs. HD patients, and additionally we wanted to determine any relationship between PTH fragments and metabolic markers of bone turnover such as the serum Carboxy-terminal telopeptides of collagen type I (βCTx), a marker of bone resorption (Bonde et al., 1995); as well as the possible role of PTH fragments in bone remodeling.