Higher osteocalcin levels and cross-links excretion in young men born withlow birth weight

As the result of accelerated growth, the final height of infants born with low birth weight (LBW) is near to the normal. Limited data are available ab out the bone density and bone turnover just after completion of skeletal de velopment. We have investigated the bone turnover and bone density in 49 ap parently healthy young LBW men (age 19-21 years: 21 born small for gestatio nal age (SGA) and 28 appropriate for gestational age (AGA)) and in 16 age-m atched controls. Bone mineral density of lumbar spine, femoral neck, and ra dius midshaft. the markers of calcium homeostasis, biochemical parameters o f bone turnover as serum osteocalcin (OC), and urinary pyridinoline (PYD) a nd deoxypyridinoline (DPD) levels were measured. Bone mineral densities of LBW subjects were not altered. Serum calcium (SGA: 2.44 +/- 0.15: AGA: 2.41 +/- 0.17, control: 2.25 +/- 0.09 mmol/liter, P < 0.05). OC (SGA: 23.4 +/- 9.9; AGA: 20.8 +/- 7.6: control: 13.3 +/- 4.6 ng/ml. P < 0.01), total alkal ine phosphatase (AP) (SGA: 201 +/- 61: AGA: 193 +/- 81, control: 117 +/- 34 IU/liter, P < 0.01), and urinary DPD/creat (ln.values: SGA: 3.10 +/- 0.48; AGA: 3.17 +/- 0.46; control: 2.58 +/- 0.57 nmol/mmol, P < 0.05) were highe r, whereas fractional excretion of calcium (SGA: 0.94 +/- 0.470; AGA: 1.03 +/- 0.51, control: 1.31 +/- 0.75%, P < 0.05) was lower in both SGA and AGA groups. PTH and 25OHD were not different. Significant correlation was obtai ned between seCa, OC, AP, DPD and birth weight of the subjects, but feCa co rrelated inversely to the birth weight. It was concluded that the bone turn over of LBW men is accelerated, but well balanced in young adulthood. Furth er investigation is needed to de scribe the possible link between accelerat ed bone turnover and hormonal homeostasis of LBW subjects.