Größenwachstum und Knochengesundheit bei Erkrankungen der Wachstumsfuge und des Knochens: Möglichkeiten und Grenzen einer GH-Therapie

Hintergrund

Genetische, parakrine und endokrine Faktoren beeinflussen das Größenwachstum und die Knochenmineralisation.

Fragestellung

Wie sind spontanes Größenwachstum und Knochengesundheit von Patienten mit seltenen Knochenerkrankungen? Kann man Wachstum und Knochengesundheit bei diesen Erkrankungen mit Wachstumshormon („growth hormone“ [GH]) verbessern?

Material und Methoden

Ergebnisse eines Expertentreffens mit Literaturrecherche zur Knochengesundheit von mit Kleinwuchs assoziierten ossären Erkrankungen und deren Therapieoptionen.

Ergebnisse

Viele Patienten mit einer Osteogenesis imperfecta sind kleinwüchsig. Eine zusätzliche Gabe von GH hat keinen Einfluss auf die Erwachsenengröße und wird derzeit nicht angewendet. Patienten mit unzureichendem Größenwachstum bei Pseudohypoparathyreoidismus (PHP) können bei Nachweis eines GH-Mangels mit GH behandelt werden und von der Therapie profitieren. Kinder mit X‑chromosomal vererbter hypophosphatämischer Rachitis haben unter der bisherigen Therapie mit Phosphat und Calcitriol einen disproportionierten Kleinwuchs. Randomisierte Therapiestudien mit GH führten zwar zu einer vorübergehenden Verbesserung der Körperhöhe, aber zu keiner signifikanten Verbesserung der Erwachsenenkörpergröße. Bei SHOX-Defizienz ist eine GH-Therapie zugelassen und hinsichtlich Köpergrößenzunahme vergleichbar effektiv wie bei Mädchen mit Ullrich-Turner-Syndrom (UTS). Zusätzlich legen Beobachtungsstudien nahe, dass eine GH-Therapie das bei UTS erhöhte Frakturrisiko reduzieren kann. Entzündung, verminderte körperliche Aktivität und Malnutrition führen bei Patienten mit juveniler idiopathischer Arthritis (JIA) zu einem Kleinwuchs mit Verlust an Muskel- und Knochenmasse. Studien konnten einen positiven Effekt von GH auf Längenwachstum, Dichte, Geometrie und Metabolismus des Knochens sowie auf die Muskelmasse zeigen. Die Therapie mit GH ist bei den Patienten mit JIA nicht zugelassen.

Schlussfolgerungen

Bei den genannten Knochenerkrankungen muss jede Wachstumsstörung individuell betrachtet werden. Neben dem Größenwachstum kann sich die GH-Therapie je nach Indikation positiv auf Stoffwechsel, Mineralsalzgehalt und Knochendichte auswirken. Zugelassene Indiktionen für eine GH-Therapie liegen bei PHP nur bei einem GH-Mangel und bei Patienten mit intrauterinem Kleinwuchs (SGA) und UTS/SHOX-Mangel vor. Neben einer Zunahme des Wachstums sollte eine Verbesserung der Knochengesundheit im Kindes- und Jugendalter als Zielparameter einer GH-Therapie diskutiert werden.

Blood pressure regulation determined by ambulatory blood pressure profiles in children and adolescents with type 1 diabetes mellitus: Impact on diabetic complications

BACKGROUND

The combination of high blood pressure and hyperglycemia contributes to the development of diabetic complications. Ambulatory monitoring of blood pressure (ABPM) is seen as standard to assess blood pressure (BP) regulation.

OBJECTIVE

We evaluated 24-hour BP regulation in 3529 children with type 1 diabetes, representing 5.6% of the patients <20 years of age documented in the DPV registry, and studied the influence of BP parameters including pulse pressure (PP) and blood pressure variability (BPV) on microalbuminuria (MA) and diabetic retinopathy (DR).

RESULTS

BP was increased in this selected cohort of children with diabetes compared to healthy German controls (standard deviation score (SDS) day: systolic BP (SBP) +0.06, mean arterial pressure (MAP) +0.08, PP +0.3; night: SBP +0.6, diastolic BP +0.6, MAP +0.8), while daytime diastolic BP (SDS -0.2) and dipping of SBP and MAP were reduced (SBP -1.1 SDS, MAP 12.4% vs 19.4%), PP showed reverse dipping (-0.7 SDS). Children with microvascular complications had by +0.1 to +0.75 SDS higher BP parameters, except of nocturnal PP in MA and diurnal and nocturnal PP in DR. Reverse dipping of PP was more pronounced in the children with MA (-5.1% vs -0.8%) and DR (-2.6% vs -1.0%). BP alteration was stronger in girls and increased with age.

CONCLUSION

There is an early and close link between 24-hour blood pressure regulation and the development of diabetic complications not only for systolic, diastolic, and mean arterial BP but also for the derived BP parameter PP and BPV in our selected patients.

Impact of overweight on effectiveness of treatment with human growth hormone in growth hormone deficient children: analysis of German KIGS data

BACKGROUND

We hypothesized that overweight children with growth hormone deficiency (GHD) demonstrate a lower response to growth hormone (GH) as a result of a misclassification since obesity is associated with lower GH peaks in stimulation tests.

METHODS

Anthropometric data, response, and responsiveness to GH in the first year of treatment were compared in 1.712 prepubertal children with GHD from the German KIGS database according to BMI (underweight=group A, normal weight=group B, overweight=group C) (median age: group A, B, C: 7.3, 7.28, and 8.4 years).

RESULTS

Maximum GH levels to tests (median: group A, B, C: 5.8, 5.8, and 4.0 µg/ml) were significantly lower in group C. IGF-I SDS levels were not different between the groups. Growth velocity in the first year of GH treatment was significantly lower in the underweight cohort (median: group A, B, C: 8.2, 8.8, and 9.0 cm/yr), while the gain in height was not different between groups. The difference between observed and predicted growth velocity expressed as Studentized residuals was not significantly different between groups. Separating the 164 overweight children into obese children (BMI>97th centile; n=71) and moderate overweight children (BMI>90th to 97th centile, n=93) demonstrated no significant difference in any parameter.

CONCLUSIONS

Overweight prepubertal children with idiopathic GHD demonstrated similar levels of responsiveness to GH treatment compared to normal weight children. Furthermore, the IGF-I levels were low in overweight children. Therefore, a misclassification of GHD in overweight prepubertal children within the KIGS database seems unlikely. The first year growth prediction models can be applied to overweight and obese GHD children.

[Bone density measurements on growing skeletons and the clinical consequences]

The measurement of bone mineral density (BMD) was established to judge the fracture risk in an individual. The most commonly used densitometric technique DXA is a two-dimensional method and reports BMD (bone mass/projection area), which increases during growth. Bone mineral density (in g/cm(3)), however, is almost stable and does not change with age or height. To analyze the data special pediatric references including data on age, sex and ethnicity are necessary as well as correction for height. Bone forms a unit with muscle. Bone responds to mechanical loading with increase in bone size and therefore adapts to the biomechanical needs. Therefore, interpretation of bone development data requires data on muscle development.The indication for bone mineral density measurement and result reporting should be made by and together with a pediatric specialist. The diagnosis of osteoporosis should not be made based solely on densitometric measurements. History of low trauma fracture is an important aspect for the definition. Besides DXA there exist further methods with advantages and disadvantages.

Successful early dietary intervention avoids obesity in patients with Prader-Willi syndrome: a ten-year follow-up

Hyperphagia is a frequent symptom in patients with Prader-Willi syndrome (PWS) and results in marked obesity with the risk of metabolic and cardiovascular complications.

AIM

To investigate whether early diagnosis of PWS and strict dietary intervention prevents excessive weight gain in patients with PWS.

PATIENTS AND METHODS

A strict fat reduced and modified carbohydrate diet consisting of 10 kcal/ cm height was provided to nine patients (seven female, two male) diagnosed early with PWS (group A). Patients were prospectively followed at our center with follow-up visits every three months. Eight patients with late diagnosis of PWS served as controls (group B). Body mass index (BMI) SDS and height SDS were compared between these two groups over a ten-year period.

RESULTS

At the age of two years height SDS and BMI SDS were significantly lower in group A (-2.9 vs -1.2, p <0.05, and BMI SDS -0.1 vs +1.8, p < 0.05). After ten years BMI SDS increased significantly to +1.2 SDS in group A, but was still significantly lower than in group B (BMI SDS +2.4), p <0.005. Patients without restrictive diet were significantly taller than patients on the diet (height SDS group A -2.8 vs group B -1.3, p < 0.05).

CONCLUSION

Early dietary treatment starting at the second year of life and continued until the age of ten years is effective in avoiding excessive weight gain in patients with PWS, but results in shorter stature. Therefore growth hormone may be a useful additional treatment in these patients.