Dietary content may prevent secondary hyperparathyroidism in female rhesus monkeys (Macaca mulatta)

Macaque laboratory chows provide relatively more calcium (Ca) and vitamin D (D) than human diets; this may influence skeletal aging. To evaluate this possibility, parameters of skeletal relevance in premenopausal and naturally postmenopausal rhesus monkeys were measured in a cross-sectional study. Serum osteocalcin (Oc) was elevated in the postmenopausal group (P < 0.01), but levels of parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD) were not different. Subsequently, in premenopausal animals, dietary Ca and/or D intake was reduced to optimal human levels for 8 weeks prior to the evaluation of the skeletal parameters. Serum 25OHD concentration was reduced (P < 0.01) and a trend (P=0.10) towards increased PTH was observed in both low D groups. In addition, serum alkaline phosphatase (ALP) levels were increased in the low Ca group (P < 0.01). In conclusion, skeletal turnover, as measured by serum Oc, was increased in naturally postmenopausal rhesus monkeys in the absence of hyperparathyroidism. Dietary D reduction causes a decline in serum 25OHD and an upward trend in PTH.