Calcium Absorption, Kinetics, Bone Density, and Bone Structure in Patients with Hereditary Vitamin D-Resistant Rickets

Abstract

Evidence from HVDRR patients reveals that calcium absorption is highly vitamin D dependent during infancy until the end of puberty, after which there is a period of about 10 yr in which mechanisms other than vitamin D-dependent ones are substantially involved in calcium absorption.

A human vitamin D receptor mutation causes rickets and impaired Th1/Th17 responses

“…This is in line with the findings by Tiosano et al, who did not detect skeletal differences between HVDRR patients and controls, using dual-energy X-ray absorption [17]. An explanation for the recovery of calcium homeostasis may result from the observation that fractional calcium absorption in late adolescents and young adults is elevated compared to young children, which is only evident in subjects on low calcium intake [17]. The exact mechanism is yet unclear but intestinal calcium uptake can be stimulated by estrogen, independently of 1,25-(OH) 2 D 3 , as shown in a rat study following 17β-estradiol treatment [18].…”

“…Moreover, no abnormalities were detected in the skeleton, using X-rays. This is in line with the findings by Tiosano et al, who did not detect skeletal differences between HVDRR patients and controls, using dual-energy X-ray absorption [17]. An explanation for the recovery of calcium homeostasis may result from the observation that fractional calcium absorption in late adolescents and young adults is elevated compared to young children, which is only evident in subjects on low calcium intake [17].…”

Clinical and Genetic Characterization of Tunisian Children with Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets

“…Evidence from HVDRR patients reveals that calcium absorption is highly vitamin D dependent during infancy until the end of puberty, after which there is a period of about 10 years in which mechanisms other than vitamin D-dependent ones are substantially involved in calcium absorption [21] . In all cases, regardless of therapy, if alopecia was present, it was unchanged by the treatment despite normalization of calcium and healing of rickets [1,12] .…”

Different Mechanisms of Intestinal Calcium Absorption at Different Life Stages: Therapeutic Implications and Long-Term Responses to Treatment in Patients with Hereditary Vitamin D-Resistant Rickets

“…However, after puberty, other mechanisms, not dependent on vitamin D, play a major role in calcium absorption, as recently shown in pubertal patients with hVDRR but near-normal PTH and calcium levels, normal bone structure and mineral density, without calcium supplementation. These patients display an adaptation to low calcium intake, with a significant increase in intestinal calcium absorption apparently occurring normally during this period of life [11]. These findings suggest that calcium supplementation after puberty may not be required for the maintenance of normal bone metabolism.…”

“…In cases of diagnosis later in childhood, high-dose parenteral calcium should initially be used, to bypass the need for intestinal absorption and to treat rickets. Normal bone metabolism and structure can then be maintained by long-term oral supplementation with calcium and vitamin D. Long-term follow-up is required, even if oral calcium supplementation after puberty does not seem to be necessary to ensure normal bone structure, mineral density and metabolism [11], as other functional outcomes, relating to bone and muscle health in particular [19], have not yet been explored in these patients.…”