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J M Wit

Publications and source records attributed to J M Wit.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Clinical drug research in children: current international guidelines. Committee for Proprietary Medicinal Products].

Drugs research in children entails a number of problems: medical-ethical, pharmacological (owing to the immaturity of the organs and the growth and development of the child) and financial (because children do not use many drugs). Consequently, children are exposed to insufficiently tested drugs and new therapeutic possibilities are withheld from them. Currently, little clinical drugs research in children is being carried out, but this is about to change. By now, European guidelines have been drawn up for the performance of clinical drugs trials according the 'good clinical practice' standards in children. In the Netherlands, a cooperative body has been set up (the Pediatric Pharmacology Network), which is to promote and coordinate paediatric pharmacological research in according with these guidelines.

Child↗
PubMed1998

De novo mutations of the growth hormone gene: an important cause of congenital isolated growth hormone deficiency?

UNLABELLED: A family with isolated growth hormone deficiency (IGHD) in two children and their mother is reported. Genetic analysis revealed a heterozygous splice site mutation in intron III of the GH-1 gene. This mutation was de novo in the mother and was transmitted in a dominant way to her offspring. CONCLUSION: De novo mutations in the GH-1 gene may be an important cause of congenital idiopathic IGHD. As these patients have normal fertility, pointing out this mutation is of great value for appropriate genetic counselling in patients with idiopathic IGHD.

Child, Preschool↗
PubMed1998

Growth hormone therapy with three dosage regimens in children with idiopathic short stature. European Study Group Participating Investigators.

OBJECTIVE: In children with idiopathic short stature (ISS) we studied the growth-promoting effect at 4 years of recombinant human growth hormone (rhGH) therapy in three dose regimens and evaluated whether increasing the dosage after the first year could prevent a decline in height velocity (HV). DESIGN: Included were 223 patients who were treated with subcutaneous administrations of rhGH 6 days per week. They were randomized to three groups: 3 IU/m2 body surface/day, 4.5 IU/m2/day, and 3 IU/m2/day during the first year and 4.5 IU/m2/day thereafter, corresponding with dosages of 0.2 and 0.3 mg/kg body weight/week, respectively. Growth was compared with a standard of 229 untreated children with ISS [ISS standard]. RESULTS: During the first year of treatment HV almost doubled and was higher with 4.5 IU/m2 than with 3 IU/m2. In the second year HV no longer differed among the groups, but increasing the dosage slowed the rate of the fall of HV. During 4 years of therapy the height SD score for age increased by a mean (SD) of 2.5 (1.0) [ISS standards], or 1.2 (0.7) (British standards), bone age increased by 4.8 (1.3) years, and predicted adult height SD score increased by 1.5 (0.7). After 4 years the results of the group with 4.5 IU/m2 were slightly better than those of the other groups. When dropouts were included in the analysis (assuming a stable height SD score after discontinuation of rhGH therapy), height gain was still significant. CONCLUSIONS: During 4 years of rhGH therapy, growth and final height prognosis improved, slightly more with 4.5 IU/m2 than with 3 IU/m2 or 3 to 4.5 IU/m2. However, bone age advanced on average 4.8 years during this period; therefore, any effect on final height will probably be modest.

Body Height↗
PubMed1998

The proxy problem: child report versus parent report in health-related quality of life research.

This study evaluates the agreement between child and parent reports on children's health-related quality of life (HRQoL) in a representative sample of 1,105 Dutch children (age 8-11 years old). Both children and their parents completed a 56 item questionnaire (TACQOL). The questionnaire contains seven eight-item scales: physical complaints, motor functioning, autonomy, cognitive functioning, social functioning, positive emotions and negative emotions. The Pearson correlations between the child and parent reports were between 0.44 and 0.61 (p < 0.001). The intraclass correlations were between 0.39 and 0.62. On average, the children reported a significantly lower HRQoL than their parents on the physical complaints, motor functioning, autonomy, cognitive functioning and positive emotions scales (paired t-test: p < 0.05). Agreement on all of the scales was related to the magnitude of the HRQoL scores and to some background variables (gender, age, temporary illness and visiting a physician). According to multitrait-multimethod analyses, both the child and parent reports proved to be valid.

Adult↗
PubMed1998

Measuring health-related quality of life in children: the development of the TACQOL parent form.

Health-related quality of life (HRQoL), conceptualized as patients' own evaluations of their health status, is an important criterion in evaluation health and health care and in the treatment of individual patients. Until now, few systematic attempts have been made to develop instruments to assess the HRQoL of children using such a conceptualization. This article describes the conceptualization and results of a study aiming to develop such an instrument for children aged 6-15 years using their parents as a proxy. The feasibility and psychometric performance of the instrument were evaluated in a study of 77 patients of the paediatric out-patient clinic of Leiden University Hospital. For each of the a priori-defined domains, a parent form scale could be constructed with satisfactory reliability and moderate correlations with the other scales. Only some of the parents indicating health status problems also signalled negative reactions to these problems. This is, in our view, a strong argument for the distinction between health status and quality of life (QoL). The correlation coefficients between the parent form and a children's questionnaire were low. Overall, the psychometric performance of the TACQOL parent form looks promising, which suggests that this instrument--with some modifications--can indeed be used to assess group differences in HRQoL in children. The results, however, should be replicated in larger samples, currently under study. The relation between parents' proxy reports on the HRQoL of their children and children's self-reports needs further investigation.

Adolescent↗
PubMed1998

Quality of life of young adults with idiopathic short stature: effect of growth hormone treatment. Dutch Growth Hormone Working Group.

The aim of the study was to evaluate whether treatment with recombinant human growth hormone (rhGH) affects the quality of life of young adults who were diagnosed as idiopathic short stature (ISS) during childhood, and whether their quality of life and aspects of the personality are different from normal. Experiences and expectations concerning rhGH treatment of the subjects and their parents were also investigated. Eighty-nine subjects were included into the study: 24 subjects (16M, 8F) were treated with rhGH from childhood, whereas 65 subjects (40M, 25F) were never treated. At the time of the interview all subjects had attained final height [mean (SD) -2.3 (0.9) SDS for Dutch references], and the age of the treated subjects was 20.5 (1.0) y, and 25.7 (3.5) y of the control subjects (p < 0.001). The level of education was similar, but the treated subjects had less often a partner compared to the control subjects (adjusted for age and gender, p < 0.001). The Nottingham Health Profile and Short Form 36 Health Survey showed no difference in general health state between treated and control subjects, and the healthy Dutch age-specific references (norm group). Although 74% of the subjects reported one or more negative events related to their height, and 61% would like to be taller, only 22% and 11% were willing to trade-off at Time Trade-Off and Standard Gamble, respectively. The personality of the subjects, which was measured by the Minnesota Multiphasic Personality Inventory, was not different from the norm group. The satisfaction with the rhGH treatment was high, as it had caused 12 (8) cm and 13 (7) cm gain in final height according to the subjects and parents, respectively. Based on initial predicted adult height (Bayley & Pinneau), this gain was only 3.3 (5.6) cm. We concluded that although the treated subjects had a partner less often when compared to the control subjects, the quality of life of subjects with ISS at adult age is normal and appears not to be affected by rhGH therapy, The treated subjects were very satisfied with the treatment, probably by overestimation of the final height gain.

Adult↗
PubMed1998

Polymorphic detection of a parthenogenetic maternal and double paternal contribution to a 46,XX/46,XY hermaphrodite.

True hermaphroditism in humans usually is associated with a 46,XX karyotype or with mosaicism in which admixtures of cells with an XX and an XY karyotype are seen. However, the mechanisms that cause such mosaicisms are poorly understood. To date, with rare exceptions, analyses of hermaphrodites have been limited mostly to cytogenetic investigations. In this report, we describe a 5-year-old patient with true hermaphroditism and a 46,XX/46,XY karyotype (ratio 38:12) in lymphocytes, suggesting involvement of two fertilization events. Microsatellite DNA polymorphisms distributed throughout the genome were analyzed, to investigate the origin of the cell lines concerned. The results are consistent with double paternal and single maternal genetic contributions. Possible mechanisms that would explain these findings are discussed. The most likely mechanism involves a single haploid ovum dividing parthenogenetically into two haploid ova, followed by double fertilization and fusion of the two zygotes into a single individual, at the early embryonic stage.

Child, Preschool↗
PubMed1998

Quality of life in short adults.

The use of (costly) growth hormone (GH) treatment in short children is often justified by the assumption that short stature considerably reduces quality of life in adults. We tested this assumption in 5 groups of short adults: 25 patients with isolated GH deficiency; 17 male patients with childhood onset renal failure; 25 women with Turner syndrome and 26 patients who were presented as a child to a paediatrician for idiopathic short stature. A group of 44 short individuals with presumably idiopathic short stature, who had not been presented to a paediatrician for short stature, was sampled from the general population ('normal shorts'). We measured quality of life in terms of socio-economic variables, the Nottingham Health Profile and time trade-off. The mean height of most groups was close to the 3rd percentile. The chance of having a partner was low for all groups, except for the normal shorts. Problems with job application were only reported in Turner syndrome. The scores on the Nottingham Health Profile were all within the normal range, but GH-deficient adults had a higher score on the domain energy than normal shorts. Women with Turner syndrome, individuals with renal failure, and those with idiopathic short stature had a wish to be taller, with an estimated reduction in quality of life of 2-4% (time trade-off). As the normal shorts did not show any sign of a reduced quality of life, we falsify the assumption of a direct relation between short stature and quality of life. The complaints of patients with idiopathic short stature around the 3rd percentile seem to be the result of unsuccessful coping strategies.

Adolescent↗
PubMed1998

Body mass index in growth hormone deficient children before and during growth hormone treatment.

Growth hormone deficiency (GHD) is associated with truncal obesity. We aimed at identifying factors that determine the body mass index (BMI) of untreated GHD children and the changes in BMI during 2 years of GH therapy in 348 Dutch GHD children registered in the National GH Registration Database. BMI was expressed as a standard deviation score (SDS). Before GH therapy, the mean (95% CI) BMI-SDS in all GHD children (0.09 (-0.05 to 0.24) SDS) was comparable to normal children. Patients with GHD due to a cranial tumour have a higher BMI (1.03 (0.69-1.36) SDS; p < 0.0001) as well as those with multiple pituitary hormone deficiencies (0.35 (0.14-0.57) SDS; p = 0.005) and patients who are in puberty at start of GH therapy (0.60 (0.13-1.08) SDS; p = 0.036). During GH therapy BMI initially decreased to reach a nadir of -0.28 (-0.35 to -0.21) SDS at 6 months. Thereafter BMI progressively increased to -0.09 (-0.18 to -0.04) SDS after 24 months. A higher initial BMI-SDS resulted in a larger decrease in BMI-SDS. We showed that this can be sufficiently explained by a regression to the mean effect.

Age Factors↗
PubMed1998

Plasma levels of insulin-like growth factor (IGF)-I, IGF-II and IGF-binding protein-3 in the evaluation of childhood growth hormone deficiency.

BACKGROUND: Traditionally, measurement of plasma IGF-I and more recently of IGFBP-3 are used to distinguish GHD from idiopathic short stature in slowly growing children, using a single blood sample. In earlier studies it was claimed that IGFBP-3 was superior to IGF-I, but more recently doubts around this claim have arisen. The role of serum IGF-II has never been studied extensively. On theoretical grounds, it can also be hypothesized that molar ratios of these peptides might be of additional value. DESIGN: Retrospective, multicentre, cohort study. PATIENTS: 96 children evaluated for short stature. METHODS: Serum IGF-I, IGF-II, IGFBP-3 and various molar ratios were, after correction for age and sex using SD scores, compared to the maximum serum GH peak after two standard provocation tests using four different methods (t-test, chi2, likelihood ratios and ROC curves). In addition, the correlations between these parameters and the short-term (1 year) and long-term (3 years) response to GH therapy were calculated. RESULTS: IGF-I performed better than IGFBP-3, but the best results were achieved by the molar ratio IGF-I:IGF-II. However, IGFBP-3 correlated better with the short-term response to GH therapy than IGF-I or the ratios, and none of the parameters investigated was found to be related to the response of long-term GH therapy.

Adolescent↗
PubMed1998

High-dose growth hormone therapy in idiopathic short stature.

This article reviews the available data on the effect of growth hormone (GH) administration on the growth of children with idiopathic short stature. The 1st year growth response appears clearly dose dependent, if the mean values from various clinical trials are combined. Dose dependency has also been shown in prospective trials. The dose dependency of the long-term growth response was less convincing in a large prospective study. The effect on final height cannot be proven with certainty in uncontrolled studies. If all available results from clinical trials are combined, a positive correlation between response and dose appears likely.

Body Height↗
PubMed1998

Effects of long-term gonadotrophin-releasing hormone analog treatment on growth, growth hormone (GH) secretion, GH receptors, and GH-binding protein in the rat.

Long-acting gonadotropin-releasing hormone (GnRH) analogs (GnRH-a) suppress gonadal steroid production and are used in precocious puberty, resulting in an arrest of pubertal development, a slower epiphyseal maturation, and a deceleration of growth, but an increased final height. However, the way that GnRH-a affect growth is not clear. GnRH-a treatment might not only affect gonadal steroid production but might also modulate the GH axis and thereby affect growth. We used a rat model to investigate the long-term effects of prepubertally started GnRH-a treatment (triptorelin) on growth, spontaneous GH secretion, hepatic GH receptors (GHR), and GH-binding protein (GHBP) and compared it with surgical gonadectomy. Triptorelin affected most parameters in the same direction as surgical gonadectomy but to a lesser extent. In females, growth was enhanced by triptorelin, baseline GH secretion was decreased, and hepatic GHR and GHBP were decreased. Apart from these effects on the GH axis, reduction of the direct inhibiting effect of estrogen on growth could be responsible for the triptorelin-induced growth. In males, triptorelin treatment enhanced body weight gain and slightly enhanced gain in length. GH peak amplitude was the only parameter of GH secretion affected and decreased, whereas GHR or GHBP were not affected. This stimulation of weight gain by long-term triptorelin treatment in male rats, which is opposite the effect of surgical gonadectomy, could indicate an interference of GnRH-a in the hormonal regulation of food intake and body weight control. We conclude that triptorelin treatment affected growth and the GH-GHR-GHBP axis in rats, more markedly in females than in males. However, triptorelin was not as effective as surgical gonadectomy.

Animals↗
PubMed1998

The role of estrogen in the control of rat osteocyte apoptosis.

We have previously shown that estrogen withdrawal by gonadotrophin-releasing hormone analogs (GnRHa) induces osteocyte death via apoptosis in human bone. Although it is likely that the increase in osteocyte death via apoptosis was related to the loss of estrogen, these experiments could not rule out a direct role for the GnRHa. Therefore, in this study, we have used a rat model of ovariectomy (OVX) to determine whether the effect of estrogen withdrawal extends to other species and to clarify the role of estrogen in the maintenance of osteocyte viability. Twelve 9-week-old rats were divided into three treatment groups: sham operated (SHAM) (n = 4), OVX (n = 4), and OVX + estrogen (E2) (25 microg/day) (n = 4). At 3 weeks following the start of treatment, tibial bones were removed. The percentage of osteocytes displaying DNA breaks, using an in situ nick-translation method, was significantly higher in the OVX group compared with the SHAM control in both cortical bone (10.04% vs. 2.31%, respectively; p < 0.0001) and trabecular bone (6.44% vs. 1.58%, respectively; p = 0.003). Addition of estrogen in the OVX animals completely abrogated the increase in osteocyte apoptosis in cortical bone (0.78%) and trabecular bone (1.17%). The percentage of apoptotic osteocytes decreased with increasing distance from the primary/secondary spongiosa interface below the growth plate in the OVX model and the OVX + E2 model. Nuclear morphology and electrophoresis of DNA confirmed the presence of apoptotic cells in the samples. In conclusion, OVX in the rat results in an increase in osteocyte apoptosis as a direct or indirect result of E2 loss. Addition of estrogen in the OVX animals prevents this increase in osteocyte apoptosis. These data confirm an important role for estrogen in the control of osteocyte apoptosis and the maintenance of osteocyte viability. Estrogen deficiency might, through compromising the viability of osteocyte networks, reduce the ability of bone to respond appropriately to loading.

Animals↗
PubMed1997

[Micropenis in children: etiology, diagnosis and therapy].

The term 'micropenis' is applied if the measured penile length is more than 2.5 standard deviations below the mean for the age; in neonates born at term this means a penile length of less than 2 cm. Micropenis is the consequence of a defect which develops after the 14th week of pregnancy. The cause may be hormonal (hypothalamo-hypophysial (hypogonadotropic hypogonadism), testicular (hypergonadotropic hypogonadism) or end organ resistance), but also iatrogenic (medication during the pregnancy). In addition, micropenis occurs as a part of a number of syndromes. The diagnostic investigation comprises history-taking, physical examination, specific hormonal testing and, if considered necessary, chromosomal and imaging examinations. In the treatment of micropenis, a trial treatment with testosterone plays an important part.

Adolescent↗
PubMed1997

Growth response and levels of growth factors after two years growth hormone treatment are similar for a once and twice daily injection regimen in girls with Turner syndrome. (Dutch Working Group on Growth Hormone).

UNLABELLED: GH is known to improve height velocity in girls with Turner syndrome (TS) but the optimal dosage regimen has yet to be defined. OBJECTIVE: We attempted to improve the growth response by trying to mimic normal pulsatile GH secretion more closely. DESIGN: In a 2-year study the effect of fractionated twice daily (BID) was compared with once daily (OD) s.c. injections of a total GH dose of 6 IU/m2/day. BID injections were administered as two-thirds at bedtime and one-third in the morning. The subjects concurrently received low dose ethinyl oestradiol (0.05 mg/kg/day, orally). SUBJECTS: Nineteen girls with TS aged 11 years or over, who were previously involved in a 10-week GH cross-over study. MEASUREMENTS: Height and bone age were evaluated in relation to untreated Turner reference data. Final height (FH) was predicted using the Bayley and Pinneau (BP) method, the modified index of Potential Height (mIPHRUS), and a recently developed Turner-specific method (PTSRUS) based on regression coefficients for height (H), chronological age (CA) and bone age (BA). Plasma levels of GH, GHBP, IGF-1, and IGFBP-3 were determined by RIA. RESULTS: After 2 years treatment the growth response expressed as HV, HVSDS, the change in HSDSCA, the gain in height over estimated untreated values and in FH prediction all showed significant improvements. Although mean values tended to be higher with OD injections, significant differences between groups were not found. Bone maturation was similar between groups and compared with untreated estimated values. Independent of treatment group, the change in HSDSCA after 2 years of GH treatment was related negatively to the baseline CA and HSDSCA, and positively to BA delay at baseline. After 18 months of GH treatment the significant decrease in GHBP plasma levels observed after 6 months was no longer significant. In contrast, IGF-1 and IGFBP-3 plasma levels and the IGF-1 to IGFBP-3 ratio increased significantly during 18 months GH therapy. None of these growth related factors showed a difference between groups in their 18 months change. Relevant side-effects were not observed during the first 2 years of GH treatment. CONCLUSIONS: The present growth data are in conformity with the data of the earlier 24-hour GH profiles. The growth response and plasma levels of growth related factors after 2 years GH on a total dose of 6 IU/m2/day in combination with low-dose oestrogens were not significantly different between the once daily and the twice daily GH injection regimen.

Adolescent↗
PubMed1997

Reference values for height, height velocity and weight in Turner's syndrome. Swedish Study Group for GH treatment.

As Northern Europeans are currently the tallest people in the world, specific growth charts for girls with Turner's Syndrome from this area are needed. Based on height and weight measurements from 598 girls with Turner's Syndrome (372 from the Netherlands, 108 from Denmark, 118 from Sweden) not treated with growth-promoting substances and without signs of spontaneous puberty, we constructed growth charts for height-for-age, height-velocity-for-age, weight-for-age, weight-for-height and Body Mass Index for age. Reference tables and regression equations for mean and standard deviation are provided allowing calculation of Standard Deviation Scores. The height and height velocity curves show a low birth length, gradual deviation from the normal percentile curves without pubertal growth spurt, and a prolonged growth until the early 20s. Mean adult height was 146.9 +/- 7.8 cm. Mean weight-for-age was lower than in normal reference children but height-adjusted weight was higher, except in infancy and early childhood. Further studies are required on the factors influencing the weight-height relationship in Turner's Syndrome.

Adolescent↗
PubMed1997

Growth before and during growth hormone treatment in children operated for craniopharyngioma.

Height and weight growth before and during treatment with human growth hormone (hGH) was studied in 46 Dutch patients treated for craniopharyngioma. Weight was expressed as body mass index (BMI, weight/height). At the time of tumor treatment mean +/- SD height standard deviation score (SDS) was -1.22 +/- 1.38 and BMI SDS was 0.56 +/- 1.32. The initial height SDS was inversely related to age (r = -0.38; p < 0.02). Before hGH treatment height SDS decreased to - 1.57 +/- 1.08 (p < 0.05) and BMI SDS increased to 1.54 +/- 1.58 (p < 0.005) during the first year after tumor treatment. Changes in height SDS correlated positively with basal prolactin (PRL) levels (r = 0.46; p < 0.05). Neither tumor localization nor treatment mode was related to changes in height SDS and BMI SDS. Forty patients were treated with hGH, started a median interval of 2.0 years after tumor treatment. At the time of the start of hGH treatment height SDS in these patients was -1.70 +/- 1.13, and BMI SDS was 1.44 +/- 1.79. During treatment with hGH, height SDS increased to -1.05 +/- 1.10 (p < 0.001) in the first, and to -0.80 +/- 1.04 (p < 0.001) in the second year. BMI SDS did not change during hGH therapy. In conclusion, there is a large variation in height SDS and BMI SDS at the time of initial presentation as well as during spontaneous growth after tumor treatment. Spontaneous growth is related to serum PRL concentrations. Treatment with hGH significantly increased height SDS during the first 2 years, whereas BMI SDS did not change.

Adolescent↗