Knemometry in childhood: a study to compare the precision of two different techniques

Knemometry is an accurate and non-invasive method of quantifying lower leg length changes. It reveals multiple fluctuations in leg length velocity over a short period of measurement, and on the basis of this it has been proposed that short-term growth is saltatory rather than a continuous phenomenon. The technical error (TE) of the technique which is generally employed, and which is subject to observer bias, ranges from 0·09 to 0·16 mm. This study was undertaken to compare the original method (OM) to a modified technique which involved measuring from a baseline value of which the operator was not aware; this technique is referred to as the random zero method (RM). Over a period of 10 months, 58 subjects were measured on 413 occasions. Overall, median TE in the RM group at 0·15 mm (P5-0, P95-0·65) was higher than the median TE in the OM group at 0·11 mm (P5-0, P95-0·37). However, the median TE over the last 3 months of 0·15 mm (P5-0·05, P95-0·87) was lower than the TE in the preceding 4 months of 0·20 mm (P5-0, P95-0·55) (WSR, p = 0·04) pointing towards the presence of an operator learning curve. The random zero method is a simple modification of the original method. It reduces observer bias but leads to a higher TE, which could explain some of the fluctuations seen between frequent knemometric measurements. Some knowledge of the length of the training period is important in the design of new studies involving knemometry; our data suggest that there should be a learning period of about 4 months if knemometry is performed as often as quoted above

The relationship between short-term changes in weight and lower leg length in children and young adults

As the knemometer is increasingly being used to study changes in lower leg length in conditions associated with weight changes it is important to clearly delineate the relationship between these two variables. Lower leg length and weight were measured in 26 children and nine adults including one pregnant woman. There was a weak but positive relationship between lower leg length and weight fluctuation in children. Daily fluctuations in weight as well as lower leg length were higher in women than men; median lower leg length fluctuation: women, 0.16 mm (P5-0, P95-0.7); men, 0.1 mm (P5-0, P95-0.48) p approximately 0.02, Wilcoxon signed-rank test. Median weight fluctuation: women 0.15 kg (P5-0, P95-0.54); men, 0.1 kg (P5-0, P95-0.5) p = 0.94 (Wilcoxon signed-rank test). Sustained weight gain in pregnancy led to a reduction in lower leg length followed by an increase which was coincident with the appearance of dependent oedema. Lower leg length changes are likely to be positively related to changes in weight when the latter are only modest in magnitude. However, greater sustained increases in weight are likely to have an opposite effect on lower leg length due to direct compression of the lower leg. Due consideration of weight is essential in longitudinal studies of lower leg length changes, especially in conditions which are associated with significant changes in weight

GNAS1 mutational analysis in pseudohypoparathyroidism

<b>OBJECTIVE:</b> Mutations of the GNAS1 gene, which is located on chromosome 20q13.11 and encodes the alpha-subunit of the stimulatory GTP-binding protein, have been identified in patients with pseudohypoparathyroidism type Ia (PHPIa) and pseudopseudohypoparathyroidism (PPHP). We have undertaken studies to determine the prevalence of GNAS1 mutations and to explore methods for their more rapid detection. <br></br> <b>METHODS:</b> Thirteen unrelated families (8 with PHPIa and PPHP patients, and 5 with PPHP patients only) were investigated for GNAS1 mutations in the 1050 base-pair (bp) region spanning exons 2-13 by single-stranded conformational polymorphism (SSCP) and DNA sequence analysis. <br></br> <b>RESULTS:</b> GNAS1 mutations were detected in 4 of the 8 families with PHPIa patients. These consisted of: two novel de novo missense mutations (Pro115Ser and Glu259Val) in two families and an identical 4 bp deletion of codons 189 and 190 resulting in a frame-shift in two unrelated families. These results expand the spectrum of GNAS1 mutations associated with this disorder and confirm the presence of a mutational hot-spot involving codons 189 and 190. SSCP analysis was found to be a specific and sensitive method that detected all 4 mutations. GNAS1 mutations were not detected in any of the PPHP only families. <br></br> <b>CONCLUSIONS:</b> The pseudohypoparathyroid disorders appear to represent a heterogeneous group with GNAS1 mutations forming the molecular aetiology in approximately 50% of pseudohypoparathyroidism type Ia families. Such mutations can be reliably identified by single-stranded conformational polymorphism and this will help to supplement the clinical evaluation of some patients and their families, particularly as the disease may not be fully penetrant

Effects of intensive chemotherapy on bone and collagen turnover and the growth hormone axis in children with acute lymphoblastic leukemia

To investigate the effects of disease and intensive chemotherapy on bone turnover and growth in children with acute lymphoblastic leukemia (ALL), a longitudinal prospective study was carried out in 22 children, aged 1.2–13.5 yr, enrolled in the Medical Research Council-funded randomized trial of childhood ALL treatment in the UK. We measured lower leg length and markers of bone formation [bone alkaline phosphatase (ALP) and procollagen type I C-terminal propeptide (PICP)], bone resorption [pyridinoline, deoxypyridinoline, and carboxyl-terminal telopeptide of type I collagen (ICTP)], soft tissue turnover [procollagen type III N-terminal propeptide (P3NP)], and the GH axis [IGF-I, IGF-binding protein-3 (IGFBP-3), IGFBP-2, and urinary GH] at 1- to 4-week intervals from diagnosis to week 27 of treatment. In addition, GH-binding protein was measured at diagnosis. <br></br> At diagnosis, mean SD scores were: bone ALP, -1.84; PICP -1.77; pyridinoline, -1.42; deoxypyridinoline, -1.66; ICTP, -0.42; P3NP, +1.45; GH, +24.4; IGF-I, -1.70; IGFBP-3, -0.88; IGFBP-2, +2.42; and GH-binding protein, -0.69. Bone ALP, PICP, and IGFBP-3 were all correlated (P 0.03). During induction and intensification, there was shrinkage of the lower leg, with decreases in PICP, pyridinoline, ICTP, and P3NP (P < 0.05), whereas IGF-I and IGFBP-3 increased (P < 0.05). After prednisolone was discontinued, bone ALP and collagen markers increased markedly (P < 0.01), but there was no significant change in IGF-I and IGFBP-3. In 12 children who received high dose iv methotrexate, postglucocorticoid increases in bone ALP and PICP were less, whereas those in ICTP and P3NP were greater, compared to levels in children who did not receive methotrexate (P < 0.05). <br></br> We conclude that ALL itself caused GH resistance and low bone turnover. During early intensive chemotherapy, further suppression of osteoblast proliferation and osteoclast activity occurred, not mediated through the systemic GH axis, probably by the direct action of prednisolone on bone. The postglucocorticoid increase in bone turnover was also independent of the GH axis and was modulated by high dose iv methotrexate, which depressed osteoblast recovery and enhanced osteoclast activity

Effects of intensive chemotherapy on bone and collagen turnover and the growth hormone axis in children with acute lymphoblastic leukemia

To investigate the effects of disease and intensive chemotherapy on bone turnover and growth in children with acute lymphoblastic leukemia (ALL), a longitudinal prospective study was carried out in 22 children, aged 1.2–13.5 yr, enrolled in the Medical Research Council-funded randomized trial of childhood ALL treatment in the UK. We measured lower leg length and markers of bone formation [bone alkaline phosphatase (ALP) and procollagen type I C-terminal propeptide (PICP)], bone resorption [pyridinoline, deoxypyridinoline, and carboxyl-terminal telopeptide of type I collagen (ICTP)], soft tissue turnover [procollagen type III N-terminal propeptide (P3NP)], and the GH axis [IGF-I, IGF-binding protein-3 (IGFBP-3), IGFBP-2, and urinary GH] at 1- to 4-week intervals from diagnosis to week 27 of treatment. In addition, GH-binding protein was measured at diagnosis. <br></br> At diagnosis, mean SD scores were: bone ALP, -1.84; PICP -1.77; pyridinoline, -1.42; deoxypyridinoline, -1.66; ICTP, -0.42; P3NP, +1.45; GH, +24.4; IGF-I, -1.70; IGFBP-3, -0.88; IGFBP-2, +2.42; and GH-binding protein, -0.69. Bone ALP, PICP, and IGFBP-3 were all correlated (P 0.03). During induction and intensification, there was shrinkage of the lower leg, with decreases in PICP, pyridinoline, ICTP, and P3NP (P < 0.05), whereas IGF-I and IGFBP-3 increased (P < 0.05). After prednisolone was discontinued, bone ALP and collagen markers increased markedly (P < 0.01), but there was no significant change in IGF-I and IGFBP-3. In 12 children who received high dose iv methotrexate, postglucocorticoid increases in bone ALP and PICP were less, whereas those in ICTP and P3NP were greater, compared to levels in children who did not receive methotrexate (P < 0.05). <br></br> We conclude that ALL itself caused GH resistance and low bone turnover. During early intensive chemotherapy, further suppression of osteoblast proliferation and osteoclast activity occurred, not mediated through the systemic GH axis, probably by the direct action of prednisolone on bone. The postglucocorticoid increase in bone turnover was also independent of the GH axis and was modulated by high dose iv methotrexate, which depressed osteoblast recovery and enhanced osteoclast activity

Biochemical markers of bone turnover

Three studies to evaluate procollagen type I C-terminal propeptide, type I collagen cross-linked telopeptide and bone alkaline phosphatase (BALP) in the assessment of bone turnover and growth in children are presented. (1) In 50 short normal children treated with placebo or growth hormone, ΔBALP after 3 months of treatment was highly correlated with height velocity response after 1 year (r = 0.67, p < 0.0001). (2) In 12 children with acute lymphoblastic leukaemia, marked changes in collagen peptides, BALP, and lower leg length velocity were seen during the first 6 months of chemotherapy. Suppression occurred during induction and the two intensification phases, with catch-up during the intervening phase (paired t-tests, p < 0.001). (3) Fourteen babies (birthweight < 1,500 g) treated with high-dose dexamethasone for bronchopulmonary dysplasia were compared with 25 non-steroid-treated babies < 1,500 g. Both collagen peptides decreased rapidly and dramatically (mean decreases 41-68%) after dexamethasone was started, accompanied by weight loss and lower leg shrinkage and followed by recovery during steroid weaning