Immunoreactive somatomedin C/insulin-like growth factor I in urine from normal subjects, pituitary dwarfs, and acromegalics

Insulin-Like Growth Factor 1 Has the Potential to Be Used as a Diagnostic Tool and Treatment Target for Autism Spectrum Disorders

Autism spectrum disorder (ASD), a heterogeneous group of neurodevelopmental disorders, is characterized by social impairment and repetitive and stereotypic behaviors. Because of the lack of approved laboratory diagnostic markers and effective therapeutic medications, it is one of the most challenging diseases. Therefore, it is urgent to explore potential diagnosis markers or therapeutic targets. Insulin-like growth factor 1 (IGF-1) is a neurotrophic growth factor that enhances brain development. IGF-1 levels in body fluids are lower in preschool children with ASD than in typically developing children, which may serve as a potential diagnostic marker. In various ASD models associated with genetic or environmental exposure, IGF-1 treatment can improve core symptoms or pathological changes, including neuronal development, neural cell survival, balance of synaptic excitation and inhibition, neuroimmunology, and oxidative stress status. In March 2023 an IGF-1 derivative was approved as the first drug for treating Rett syndrome, an ASD-related neurodevelopmental disorder, to improve fundamental symptoms such as social communication. Thus, in this review, we present accumulating evidence of altered IGF-1 levels in ASD patients and the possible mechanisms, as well as evidence that IGF-1 treatment improves the pathophysiology in various ASD models. IGF-1 has the potential to be an early diagnosis marker and an effective therapeutic for ASD.

Serum and urine insulin-like growth factor-1 as biochemical growth maturity indicators

INTRODUCTION

Biochemical markers are agents directly involved in bone growth and remodeling and can be quantitatively evaluated from various biologic fluids. The aim of this study was to assess the changes in the levels of insulin-like growth factor-1 (IGF-1) in serum and urine as a growth maturity indicator and to compare them with the cervical vertebral maturation radiographic stages.

METHODS

The study was conducted with 72 female subjects aged 8 to 20 years. Cervical vertebral maturation stages, and serum and urine IGF-1 levels were recorded for all subjects, and the subjects were equally divided into the 6 cervical vertebral maturation groups. Median values of IGF-1 for each stage of cervical vertebral maturation were calculated and statistically compared with those of the other stages.

RESULTS

The levels of serum and urine IGF-1 at stage 4 of cervical vertebral maturation were significantly higher than those from the other stages (P <0.01). Stage 4 corresponded to a mean age of 13.67 years. A significant correlation was observed between serum and urine IGF-1 (P <0.001).

CONCLUSIONS

Urine IGF-1 follows the growth curve similar to serum IGF-1. Thus, urine IGF-1 may be regarded as a promising noninvasive tool for growth assessment. Further research is necessary to validate these results in a different population and with a larger sample.

IGF-I abuse in sport: current knowledge and future prospects for detection

As the tests for detecting growth hormone (GH) abuse develop further, it is likely that athletes will turn to doping with insulin-like growth factor-I (IGF-I). IGF-I mediates many of the anabolic actions of growth hormone. It stimulates muscle protein synthesis, promotes glycogen storage and enhances lipolysis, all of which make IGF-I attractive as a potential performance-enhancing agent. Pharmaceutical companies have developed commercial preparations of recombinant human IGF-I (rhIGF-I) for use in disorders of growth. The increased availability of rhIGF-I increases the opportunity for athletes to acquire supplies of the drug on the black market. The long-term effects of IGF-I administration are currently unknown but it is likely that these will be similar to the adverse effects of chronic GH abuse. The detection of IGF-I abuse is a challenge for anti-doping organisations. Research has commenced into the development of a test for IGF-I abuse based on the measurement of markers of GH action. Simultaneously, the effects of rhIGF-I on physical fitness, body composition and substrate utilisation in healthy volunteers are being investigated.

Urinary GH and IGF-I excretion in nine year-old children: relation to sex, current size and size at birth

OBJECTIVES

To study the relationship of 24-hour urinary growth hormone (GH) and IGF-I excretion in childhood to sex and body size. To test the hypothesis that small size at birth followed by postnatal catch-up growth is associated with elevated IGF-I production.

DESIGN AND SUBJECTS

Follow-up study of a cohort of 183 healthy children born in Salisbury, UK.

MEASUREMENTS

Weight and height, 24-h urinary growth hormone (uGH) and IGF-I (uIGF-I) excretion, and systolic and diastolic blood pressures.

RESULTS

At 9 years of age, 24-h uIGF-I excretion, but not uGH excretion, was strongly related to current weight (P < 0.001) and height (P < 0. 001). Urinary GH and IGF-I excretion were positively correlated (r = 0.15, P = 0.05). Boys excreted more uIGF-I per unit uGH than girls (uIGF-I/uGH molar ratio 32.1 compared to 21.0; P for difference = 0. 002). There were no significant relationships of uGH, uIGF-I or uIGF-I/uGH molar ratio with birthweight, birthlength or head circumference at birth, nor with blood pressure at 9 years. 'Catch-up' growth, indicated by an increase in height SD scores between birth and 9 years, was associated with higher IGF-I excretion (P = 0.01) and occurred in children with taller parents (P < 0.001).

CONCLUSIONS

Boys appear to be more sensitive to GH than girls, generating more uIGF-I in relation to uGH. Urinary IGF-I excretion at 9 years is related to both absolute height and to the degree of catch-up in height from birth. Our results suggest that IGF-I production is strongly influenced by genetic factors, but also by either the degree to which intrauterine growth falls short of genetic growth potential, or the process of postnatal catch-up growth that follows.

Relationship between serum and urinary insulin-like growth factor-I through childhood and adolescence: their use in the assessment of disordered growth

OBJECTIVE

Serum insulin-like growth factor-I (sIGF-I) measurement as an index of growth hormone status has become a common test in the investigation of disordered growth. IGF-I may also be measured in the urine. The aims of this study were to investigate the correlation between serum and urinary IGF-I in normal children and compare their use in the evaluation of growth disorders.

DESIGN

Normal ranges for serum and urinary IGF-I were devised from a cross-sectional study of normal schoolchildren. These were then used to assess the sensitivity and specificity of serum and urinary IGF-I in the diagnosis of childhood GH deficiency.

PATIENTS

A cohort of 333 (M = 156, F = 177) healthy schoolchildren aged 5-19 years were recruited and data previously collected from 22 growth hormone deficient (GHD) and 47 short normal (SN) children were compared with those of the normal children.

MEASUREMENTS

Height, weight and pubertal status were assessed in all children. Serum IGF-I (sIGF-I) (n = 305) and total amount of urinary IGF-I excreted overnight (TuIGF-I) (n = 205) were measured by RIA using excess IGF-II to block the interference of IGFBPs.

RESULTS

Serum IGF-I was loge transformed and overall levels (geometric mean +/- 1 tolerance factor) were higher in females than males (F: 569 (329, 985) micrograms/l; M: 398 (227, 696) micrograms/l). LogeIGF-I correlated with age (F: r = +0.76, P < 0.001, M: r = +0.71, P < 0.001) and was significantly affected by both sex and Tanner stage of puberty (TS) (both P < 0.001). The distribution of TuIGF-I was normalized by performing a square root transformation (square root of TuIGF-I). square root of TuIGF-I was correlated with age (F: r = +0.36, P < 0.001; M: r = +0.5, P < 0.001) and was significantly affected by TS (P < 0.001). In both sexes there was a highly significant correlation between logeIGF-I and square root of TuIGF-I (F: r = +0.39, P < 0.001; M: r = +0.41, P < 0.001). Using the third centile of our normal ranges as a cut off to identify GHD, sIGF-I had a sensitivity of 82% and specificity of 62%, whereas TuIGF-I had a sensitivity of 18% and specificity of 79%.

CONCLUSIONS

This study demonstrates that although urinary IGF-I has no place in the diagnosis of growth disorders, in normal children there is a highly significant relationship between serum and urinary IGF-I with levels of each changing in a similar manner through childhood and adolescence. Thus, TuIGF-I could be used as a valid surrogate for sIGF-I in the physiological assessment of the relationship between IGF-I status and the normal growth process.

Acromegaly

Acromegaly can be a serious, chronic, debilitating condition. The disease is often missed for years, resulting in significantly delayed diagnosis. This article reviews recent advances in our understanding of acromegaly and the impact of current approaches on the diagnosis and monitoring of patients with this disorder.

Insulin-like growth factor-I and insulin-like growth factor-binding proteins in the nephrotic syndrome

Similar to findings in the nephrotic syndrome in humans, rats with the doxorubicin-induced nephrotic syndrome (which resembles minimal change disease) have reduced serum levels of insulin-like growth factor-I (IGF-I). This is mainly caused by glomerular ultrafiltration of IGF-I-containing binding protein complexes, primarily of a molecular weight of approximately 50 kilodaltons, and urinary losses of the peptide. Despite urinary excretion of IGF-binding protein (IGFBP)-2, serum levels are increased more than twofold in the nephrotic syndrome compared with controls, because of increased synthesis of this binding protein by the liver. In contrast, the liver synthesis of IGFBP-3, the predominant binding protein in normal serum, is unchanged in the nephrotic syndrome. However, binding and serum levels of IGFBP-3 are reduced in nephrotic rat serum, apparently due to proteolytic degradation of IGFBP-3. The glomerular ultrafiltration of IGF-I, which leads to biologically significant IGF-I concentrations of about 1.35 nM in proximal tubule fluid, may have metabolic consequences, such as increased tubular phosphate absorption. Hypothetically, tubule fluid IGF-I may also contribute to progressive tubulointerstitial fibrosis which is sometimes present in protractive nephrotic glomerulopathies. The profound changes in the IGF-I/IGFBP system in the nephrotic syndrome may also contribute to systemic metabolic abnormalities and growth failure.

Fetal urinary insulin-like growth factor I and binding protein 3 in bilateral obstructive uropathies

Fetal urinary concentrations of insulin-like growth factor I (UIGF-I) and binding protein 3 (UIGFBP-3) were determined in patients with prenatal diagnosis of bilateral obstructive uropathy. Patients were retrospectively assigned to three groups, on the basis of outcome: group 1, termination of pregnancies (n = 11) with sonographic evidence of severe oligohydramnios or renal dysplasia, confirmed at histological examination; group 2, patients (n = 10) with postnatal plasma creatinine > 50 mumol/l at the age of 1 year (1 yr-pCreat); and group 3, patients (n = 16) with 1 yr-pCreat < or = mumol/l. The results show a significant increase in UIGF-I and UIGFBP-3 in groups 1 (18,159 +/- 9083 pg/ml; 2657 +/- 669 ng/ml) and 2 (1574 +/- 847 pg/ml; 176 +/- 50 ng/ml) in comparison with group 3 (35 +/- 6 pg/ml; 21 +/- 2 ng/ml). UIGF-I and UIGFBP-3 were significantly correlated with postnatal plasma creatinine, and were both sensitive (90 per cent; 80 per cent) and specific (88 per cent; 88 per cent) for prediction of elevated 1 yr-pCreat (> 50 mumol/l). Fetal urinary IGF-I and IGFBP-3 are increased in severe fetal bilateral obstructive uropathy, possibly reflecting tubular dysfunction or/and increased synthesis consequent upon fetal kidney injury. Their predictive value for postnatal renal function needs further assessment.

Pharmacokinetics of recombinant human insulin-like growth factor-1 in dialysis patients

Six maintenance hemodialysis (MHD), six continuous ambulatory peritoneal dialysis (CAPD) and six normal adults underwent pharmacokinetic studies of insulin-like growth factor-1 (IGF-1). Each subject received two separate subcutaneous injections of recombinant human IGF-1 (rhIGF-1) (50 or 100 micrograms/kg) in random order separated by 7 to 21 days. Two different responses were observed. With the 50 micrograms/kg dose, serum IGF-1 levels and the pharmacokinetic parameters were not different between the three groups. With the 100 micrograms/kg dose, peak serum IGF-1 concentrations were significantly greater in the MHD and CAPD patients than in normals. However, by 12 to 14 hours after injection, serum IGF-1 was not different in the three groups. Although the Tmax, area under the curve and serum clearance of IGF-1 were similar in the three groups, the half-life and volume of distribution of rhIGF-1 was significantly decreased in both MHD and CAPD patients. These data indicate that IGF-1 pharmacokinetics are abnormal in maintenance dialysis patients.