Relationship of somatomedin-C concentration to bone age in boys with constitutional delay of growth.

Serum somatomedin-C (Sm-C) levels increase sharply during puberty, leading to difficulty in the interpretation of Sm-C values obtained from children who exhibit a discrepancy between chronological age (CA) and pubertal development. To evaluate the utility of assessing Sm-C levels on the basis of bone age (BA), we measured serum Sm-C levels in 44 boys with constitutional delay of growth (CDG). Levels of Sm-C were compared with the normative data of the Nichols Institute Reference Laboratories (NIRL), Los Angeles, by age category, substituting BA for CA. We found the mean Sm-C level in boys with CDG to be lower than that for NIRL normal subjects in each age category for both CA and BA, but the regression curve for Sm-C levels based on BA more closely approximated the NIRL regression curve than did the curve based on CA. The rise in Sm-C levels observed in NIRL normal subjects between CA 13 to 14 years is delayed in boys with CDG until CA 15 to 17 years only when a correction for BA is not made. We conclude that in boys with CDG, Sm-C levels should be interpreted on the basis of BA rather than CA, especially during the peripubertal period. The observation of blunted Sm-C levels in all age categories, even when BA was used, suggests that short children with presumed CDG may be at high risk for a "nonclassic" form of growth hormone deficiency.

Russell-Silver syndrome and hypopituitarism. Patient report and literature review.

Russell-Silver syndrome (RSS) is a sporadic form of prenatal onset dwarfism with typical facial features, variable asymmetry, and linear growth 3 to 4 SDs below the mean. Endocrinologic studies are usually normal; however, six cases of RSS with growth hormone deficiency have been reported, three of which had additional pituitary abnormalities. We describe another case, a 7-year-old girl with RSS and deficiencies of growth hormone, corticotropin, and thyroid-stimulating hormone. Replacement therapy including growth hormone resulted in an improved growth velocity, though twice the usual dose of growth hormone was required and short stature persisted. Since growth hormone secretion is usually normal in RSS, the existence of individuals with RSS phenotype and hypopituitarism including growth hormone deficiency suggests etiologic heterogeneity. We recommend that those individuals with RSS phenotype and a continuous significant decline in height velocity be investigated for pituitary abnormalities. Unusually high replacement doses of growth hormone may be required to overcome deficiency.

Yogurt. Contributory factor in development of nutritional rickets.

Vitamin D deficient rickets occurred in a 15-month-old black girl for whom yogurt had been substituted for milk products. Investigation determined that commercially available yogurt contains no vitamin D, and that this fact is not generally recognized by lay persons and health professionals. Use of yogurt as a major source of nutritional intake in infants and young children may be a contributory factor in development of vitamin D deficiency rickets.

Radioimmunoassay for type I procollagen in growth hormone-deficient children before and during treatment with growth hormone.

Type I procollagen concentrations were measured by radioimmunoassay in sera from 14 growth hormone-deficient children before and during 12 months of treatment with human growth hormone. Basal procollagen levels were lower than those of control children and comparable to those of normal adults. With treatment, the mean procollagen level increased into the range of the control children and was significantly greater than the baseline level at 1, 2, 3, and 12 months (p less than 0.01; p less than 0.05). Although there was no significant statistical correlation between the growth velocity during treatment and the serum procollagen level, there was a suggestion that a high basal procollagen may be predictive of a less than optimal response to human growth hormone.

Renal-resistant hormonoplethoric hypoparathyroidism with evidence for a defective response to cAMP.

A 15.5-yr-old black male is reported with hypocalcemia, hyperphosphatemia, and severe osteitis fibrosa cystica. While hypocalcemic and hyperphosphatemic, the circulating parathyroid hormone (PTH) level and urinary cAMP excretion were increased. An infusion of exogenous PTH produced a normal maximal excretion of urinary cAMP but failed to increase phosphate excretion. Correction of the hypocalcemia by administration of 200,000 U vitamin D daily lowered the endogenous PTH level and basal excretion of cAMP to normal; at that time, infusion of PTH produced both a normal rise in urinary cAMP and a normal phosphaturic response. This pattern of response suggests pseudohypoparathyroidism with a calcium-sensitive defect in renal phosphate transport distal to the PTH receptor adenyl cyclase mechanism, producing hyperphosphatemia, hypocalcemia, and secondary hyperparathyroidism. The osteitis fibrosa cystica was presumably due to the increased PTH, suggesting that resistance to PTH was present in kidney but not bone.

Decreased cortical thickness & osteopenia in children with diabetes mellitus.

A recent study using the photon absorption technique has revealed a high frequency of significant bone loss in diabetic adults regardless of age or duration of diabetes. In this study 107 diabetic children age 4-18 were studied using cortical bone thickness and skeletal maturation as indicators of bone development. Overall, 25% of all diabetic children had cortical thickness values below the five percent limit for normal children. This was more common in boys than girls and was unrelated to duration of diabetes. A modest increase in delayed skeletal maturation did not account for the cortical thinning and osteopenia observed. The cause of the osteopenia of diabetic children remains an enigma.