Influence of Secondary Hyperparathyroidism Induced by Low Dietary Calcium, Vitamin D Deficiency, and Renal Failure on Circulating Rat PTH Molecular Forms

Moderate/subclinical calcium deficiency attenuates trabecular mass, microarchitecture and bone growth in growing rats

Adequate dietary calcium (Ca) intake is essential for bone accretion, peak bone mass (PBM) attainment, bone quality and strength during the mammalian growth period. Severe Ca deficiency during growing age results in secondary hyperparathyroidism (SHPT) and poor bone quality and strength. However, the impact of moderate Ca deficiency during rats early growth period on bone health and the reversibility with supplementing calcium later in adult life remains unclear. Female Sprague-Dawley (SD) rats (postnatal 28th day, P28) were initiated either with a moderate calcium-deficient diet (MCD, 0.25% w/w Ca) or a control diet (0.8% w/w Ca, control group) till P70. Thereafter, MCD rats were continued either with MCD diet or supplemented with calcium diet (0.8% w/w Ca, calcium supplemented group, CaS) till P150. Another group (control rats) were fed 0.8% w/w Ca containing diet from P28 till P150.

MCD group, as compared to the control group, had significantly reduced serum ionized Ca and procollagen type 1 N-terminal propeptide (P1NP) at P70 while no significant change was observed in serum corrected Ca, inorganic phosphate (P), alkaline phosphatase (ALP), 25-hydroxy vitamin D [25(OH)D], intact parathyroid hormone (iPTH), and urinary C-terminal telopeptide of collagen 1 (CTX-1), Ca, and P. Femoral and tibial metaphysis in MCD rats had significantly reduced linear growth, cortical and trabecular volumetric BMD (vBMD), trabecular microarchitecture (BV/TV%, trabecular thickness, separation and number, structural model index and connectivity density), cortical thickness, and bone stiffness despite the absence of secondary hyperparathyroidism (SHPT). Continued MCD at P70–P150 results in persistence of compromised bone strength while calcium supplementation (CaS group) improved all the parameters related to bone strength and microarchitecture. Our results indicate that uncorrected moderate/subclinical calcium deficiency in growing rats can result in poor bone quality and strength despite the absence of SHPT. This finding could have relevance in children with poor calcium intake in childhood and adolescence.

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Moderate Ca intake impairs bone growth and stiffness in critical growth phase via subclinical Ca deficiency.

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Ca supplementaion reverses the effects subclinical Ca deficiency on bone health.

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Conclusively, moderate Ca intake imposes different effects on the bone at different phases of life.

Vitamin D Status in Infants during the First 9 Months of Age and its Effect on Growth and Other Biochemical Markers: A Prospective Cohort Study

Background:

Despite food fortification policies in many countries and recommendations for Vitamin D supplementation of at-risk groups, Vitamin D deficiency (VDD) and infantile rickets remain major public health challenges in many developed and developing countries.

Materials and Methods:

Ninety-six participants at birth were enrolled and followed up until 9 months of age. Serum 25OHD was estimated in cord blood at birth and at 14 ± 1 weeks of life. Seventy-seven participants were followed up at 9 months for estimation of serum 25OHD, parathyroid hormone (PTH), alkaline phosphatase (ALP), calcium, and phosphorus. VDD was defined as serum 25OHD <15 ng/mL as per USIOM guidelines.

Results:

Serum 25OHD levels at 9 months of age (15.78 ± 8.97 ng/mL) were significantly increased in comparison to the level of 3 months of age (14.04 ± 7.10 ng/mL) and at birth (8.94 ± 2.24 ng/mL). At birth, all the participants (77) were deficient in 25OHD levels. It was found that 16/94 (17%) and 19/77 (24.7%) participants at 3 and 9 months of age, respectively, became Vitamin D sufficient without any Vitamin D supplementation. There was a significant inverse correlation between serum 25OHD and PTH concentration (r = −0.522, P < 0.001), serum 25OHD and ALP (r = −0.501, P < 0.001). It was found that reduction in serum Vitamin D level to <10.25 ng/mL results in a surge of serum PTH.

Conclusion:

VDD is common from birth to 9 months of age but incidence decreases spontaneously even without supplementation. Furthermore, a large number of babies may be falsely labeled as Vitamin D deficient with currently followed cutoffs. Hence a new cutoff for VDD needs to be established for neonates and infants.

Vitamin D deficiency in infants aged 1 to 6 months

Purpose

The aim of this study was to recognize the state of vitamin D among healthy infants aged 1 to 6 months in South Korea, and also to identify the risk factors affecting the level of vitamin D.

Methods

A total of 117 infants were enrolled in this study for 12 months, from March 1, 2011 to February 29, 2012. Serum levels of 25-hydroxyvitamin D (25[OH]D), calcium, phosphorus, and alkaline phosphatase were measured and data including birth weight, body weight, sex, feeding pattern, delivery mode, siblings and maternal age and occupation were collected. Data was mainly analyzed with independent t-test model.

Results

We determined that the prevalence of vitamin D deficiency (serum 25[OH]D<20 ng/mL [50 mmol/L]) was 48.7% in the population investigated. Particularly in breastfed infants, the prevalence of vitamin D deficiency was strikingly high (90.4%). The mean serum level of 25(OH)D in breastfed infants was lower than that of formula fed infants (9.35 ng/mL vs. 28.79 ng/mL). Also female infants showed lower mean serum level of 25(OH)D than male. Mean serum values of calcium and phosphorus had positive correlation with vitamin D state (P<0.001).

Conclusion

Vitamin D deficiency was found to be very common in infants aged 1 to 6 months in South Korea, and breast feeding was the most critical risk factor of vitamin D deficiency. Therefore we suggest to start vitamin D supplementation in South Korea, as soon as possible, to all infants, including breastfed and female infants.