Activity of GH/IGF-I axis in trauma and septic patients during artificial nutrition: different behavior patterns?

Insulin-like Growth Factor I and its binding protein 3 in sepsis

OBJECTIVE

To investigate the Growth Hormone (GH)/Insulin-like Growth Factor-I (IGF-I) axis and identify the factors that determine IGF-I levels in adult septic patients of variable severity, i.e., with sepsis, severe sepsis or septic shock, in the acute phase of disease.

DESIGN

In 107 consecutive septic patients (44 with sepsis, 13 with severe sepsis, and 50 with septic shock), GH, IGF-I, Insulin-like Growth Factor Binding Protein-3 (IGFBP-3), insulin, cortisol, albumin, thyroid hormones, C-reactive protein and interleukin-6 serum levels were measured once within 48 h after onset of a septic episode. Twenty-nine healthy volunteers served as controls.

RESULTS

IGF-I and IGFBP-3 levels were decreased in patients with sepsis and severe sepsis (versus controls), decreasing further in patients with septic shock (versus sepsis). IGF-I levels were positively related to IGFBP-3, albumin, triiodothyronine and thyroxine, and inversely related to cortisol, sepsis severity, C-reactive protein, interleukin-6 and age. In multiple regression analysis, IGF-I levels were independently related to IGFBP-3 and albumin (lower in patients with decreased IGFBP-3 and albumin levels) (p<0.001 and p=0.01, respectively), and cortisol (lower in patients with increased cortisol levels) (p=0.04). IGFBP-3 accounted for most of the variance explained by the model (R(2)=0.519). GH levels were not related to IGF-I levels or mortality. IGF-I and IGFBP-3 levels were not associated with mortality.

CONCLUSIONS

The GH/IGF-I axis is severely disrupted in septic patients. IGFBP-3 is the major determinant of IGF-I levels.

Performance-enhancing sports supplements: role in critical care

Many performance-enhancing supplements and/or drugs are increasing in popularity among professional and amateur athletes alike. Although the uncontrolled use of these agents can pose health risks in the general population, their clearly demonstrated benefits could prove helpful to the critically ill population in whom preservation and restoration of lean body mass and neuromuscular function are crucial. Post-intensive care unit weakness not only impairs post-intensive care unit quality of life but also correlates with intensive care unit mortality. This review covers a number of the agents known to enhance athletic performance, and their possible role in preservation of muscle function and prevention/treatment of post-intensive care unit weakness in critically ill patients. These agents include testosterone analogues, growth hormone, branched chain amino acid, glutamine, arginine, creatine, and beta-hydryoxy-beta-methylbutyrate. Three of the safest and most effective agents in enhancing athletic performance in this group are creatine, branched-chain amino acid, and beta-hydryoxy-beta-methylbutyrate. However, these agents have received very little study in the recovering critically ill patient suffering from post-intensive care unit weakness. More placebo-controlled studies are needed in this area to determine efficacy and optimal dosing. It is very possible that, under the supervision of a physician, many of these agents may prove beneficial in the prevention and treatment of post-intensive care unit weakness.

Normal age-dependent values of serum insulin growth factor-I: results from a healthy Italian population

Serum IGF-I levels were measured in 547 non-hypopituitaric, non-acromegalic healthy subjects of both sexes in Italy to develop reference values in relation to age and sex. Participant subjects were stratified in three age classes (25- 39, 40-59 and >or=60 yr) and IGF-I assay was carried out by double-antibody radio immunoassay. Pearson's correlation coefficient between age and IGF-I values was calculated by sex and predefined age ranges. IGF-I levels significantly decreased with age (p<0.001, Kruskal-Wallis test) while sex was not a significant factor. The median IGF-I levels were 206 ng/ml in the 25-39 yr range, 147 ng/ml in the 40-59 yr range and 103 ng/ml in the >or=60 yr range. Pearson's correlation coefficient confirmed the negative correlation between age and IGF-I levels in the total sample of subjects (r=-0.529). The r coefficient between age and IGF-I levels did not differ between sexes (r=-0.570 in males and r=-0.529 in females), thus reflecting no sex-effect on IGF-I levels decline over years. No correlations were found in the 25-39 yr range (r=-0.036) or in the 40-59 yr range (r=-0.080) either, while in subjects aged >60 yr, IGF-I levels tended to further decrease with increased age (r=0.389). Ranges of normal values set at the 2.5th-97.5th percentile in the three age ranges were 95.6-366.7 ng/ml between 25 and 39 yr, 60.8-297.7 ng/ml between 40 and 59 yr and 34.5-219.8 ng/ml in subjects aged >or=60 yr. This study may contribute to the development of age-specific reference ranges for IGF-I determination in serum of normal subjects of both sexes in Italy.

Metabolic support in sepsis and multiple organ failure: more questions than answers

The metabolic support of critically ill patients is a relatively new topic of active research and discussion, and surprisingly little is known about the effects of critical illness on metabolic physiology and activity. The metabolic changes seen in critical illness are highly complex, and how and when to treat them are only just beginning to be determined. Studies have demonstrated that the acute phase and the later phase of critical illness behave differently from a metabolic point of view for many organs, and while many of the alterations in metabolism seen during early critical illness may be appropriate and beneficial responses to cellular stress, whether this is true for all the metabolic alterations in all forms of critical illness is unclear. Currently we face more questions than answers, and further study is needed to elucidate the various components of the metabolic response to acute and chronic critical illness and to develop better techniques to assess and monitor these changes so that we can determine which therapeutic approaches should be used in what combinations and in which patients.

Differential influence of open surgery and sepsis on the circulating insulin-like growth factors and their binding proteins as representative metabolic markers

OBJECTIVES

In critical illnesses and stress conditions many endocrine systems are disturbed. In the current study we determined the influence of open surgery, post-operative sepsis and its early therapy on the components of the insulin-like growth factor (IGF) system in patients with malignant gastric or pancreatic tumors.

DESIGN AND METHODS

Twenty-one patients and eighty-one age- and sex-matched healthy subjects were included in this study. IGF-I, IGF-II, IGF binding proteins (IGFBPs), cortisol, insulin and protein concentrations (total, albumin and IgG) were determined pre-operatively, post-operatively, when sepsis was diagnosed and 48 h after initiating therapy.

RESULTS

The concentrations of circulating IGF-I, IGF-II and IGFBP-3 were significantly lower in pre-operative patients compared to healthy subjects. Sepsis caused a further decrease in IGF-I and IGFBP-3 but an increase in IGFBP-1, IGFBP-2 and IGFBP-4 resulting in a redistribution of IGF molecules from ternary to binary complexes.

CONCLUSIONS

The presence of malignant gastric or pancreatic tumors followed by post-operative sepsis caused a serious misbalance in components of the IGF system which failed to recover during the time of our longitudinal study.

Systemic metabolic effects of combined insulin-like growth factor-I and growth hormone therapy in patients who have sustained acute traumatic brain injury

OBJECT

Hypermetabolism, hypercatabolism, refractory nitrogen wasting, hyperglycemia, and immunosuppression accompany traumatic brain injury (TBI). Pituitary dysfunction occurs, affecting growth hormone (GH) and plasma insulin-like growth factor-I (IGF-I) concentrations. The authors evaluated whether combination IGF-I/GH therapy improved metabolic and nutritional parameters after moderate to severe TBI.

METHODS

The authors conducted a prospective, randomized, double-blind study comparing combination IGF-I/GH therapy and a placebo treatment. Ninety-seven patients with TBI were enrolled in the study within 72 hours of injury and were assigned to receive either combination IGF-I/GH therapy or placebo. All patients received concomitant nutritional support. Insulin-like growth factor-I was administered by continuous intravenous infusion (0.01 mg/kg/hr), and GH (0.05 mg/kg/day) was administered subcutaneously. Placebo control group patients received normal saline solution in place of both agents. Nutritional and metabolic monitoring continued throughout the 14-day treatment period. The two groups did not differ in energy expenditure, nutrient intake, or use of insulin treatment. The mean daily serum glucose concentration was higher in the treatment group (123 +/- 24 mg/dl) than in the control group (104 +/- 11 mg/dl) (p < 0.03). A positive nitrogen balance was achieved within the first 24 hours in the treatment group and remained positive in that group throughout the treatment period (p < 0.05). This pattern was not observed in the control group. Plasma IGF-I concentrations were above 350 ng/ml in the treatment group throughout the study period. Overall, the mean plasma IGF-I concentrations were 1003 +/- 480.6 ng/ml in the treatment group and 192 +/- 46.2 ng/ml in the control group (p < 0.01).

CONCLUSIONS

The combination of IGF-I and GH produced sustained improvement in metabolic and nutritional endpoints after moderate to severe acute TBI.

Activity of the growth hormone/insulin-like growth factor-I axis in critically ill children

Critical illness has an important impact on the human endocrine system. Very few studies have been performed to elucidate the alterations of the GH/IGF-I axis in acutely ill children. The aim of this study was to investigate several parameters of this axis in children with trauma (TRA) and sepsis (SEP) requiring admission to the pediatric intensive care unit (PICU). A total of 16 children, ten with TRA and six with SEP (age 1-10 years) as well as 18 healthy children (CS) of similar age and gender were included in the study. Two children, one with TRA and one with SEP, died. Serum IGF-I and -II, IGFBP-1 and -3, and GH levels were measured on days 1, 3 and 7 after admission. GH levels were higher in the patients than in CS (p = 0.04), with no difference between TRA and SEP, and were elevated during PICU stay (p = 0.05). Serum IGF-I, -II and IGFBP-3 were lower in the patients than in CS (p = 0.03, 0.02 and 0.001, respectively) with a tendency to increase up to day 7. Finally, IGFBP-1 levels were similar in the patients and CS. These findings indicate that critically ill children are characterized by low levels of IGF-I and -II as well as IGFBP-3 accompanied by elevated levels of GH, probably reflecting the development of peripheral GH resistance. No significant differences were found between the different catabolic conditions, sepsis and trauma.

Impaired GH secretion to provocative stimuli in two families with hypocalciuric hypercalcaemia

OBJECTIVE

To determine whether hypercalcemia per se might be responsible for an impairment in GH secretion.

DESIGN

Prospective study.

PATIENTS

Six subjects of two unrelated families with familial hypocalciuric hypercalcaemia (FHH), an autosomal dominant disorder due to inactivating mutations in the calcium receptor gene, leading to an increase in serum calcium levels and inappropriately normal serum PTH concentrations. Forty normal subjects, matched for sex and age served as controls.

MEASUREMENTS

Serum GH concentrations were measured after GHRH-Arginine (GHRH-Arg) stimulation test; serum IGF-I, ACTH, cortisol, FT4, FT3, TSH, PRL, LH, FSH levels were measured under basal conditions.

RESULTS

All subjects (two male, four female, age range 24-74 years) had increased serum ionized calcium levels (range 1.36-1.56 mmol/l) and five of six patients had normal PTH levels (range for all patients was 14-68 ng/l). Basal serum GH concentrations ranged from 0.1 to 7.0 micro g/l. Mean serum GH secretory peak after GHRH-Arg stimulation test was reduced in five subjects (mean 9.3 +/- 3.6 microg/l, P < 0.006 vs. Controls, mean 67.0 +/- 44.0 microg/l, cut-off, 16.0 microg/l) and normal in one subject (38.7 microg/l). However, serum IGF-I levels were reduced only in two patients (29 and 57 microg/l) and normal in four subjects (range 127-208 microg/l). The basal secretion of the other anterior pituitary hormones was within their normal ranges.

CONCLUSIONS

The results of the present study support the concept that elevated serum calcium levels impair GH secretion. However, the clinical relevance of GH deficiency in FHH remains to be elucidated.

The role of visceral proteins in the nutritional assessment of intensive care unit patients

PURPOSE OF REVIEW

This review analyses the recently published literature focusing on nutritional assessment in intensive care unit patients. The metabolic response to nutritional intervention is difficult to evaluate in critically ill patients whose body weight is influenced largely by massive fluid administration or losses. Visceral protein plasma levels have been proposed for this purpose, because they reflect hepatic synthesis in response to nutrient supply. However, in acute inflammatory states, liver activity is converted to the synthesis of acute-phase response proteins, resulting in a dramatic drop in visceral proteins, despite nutritional support.

RECENT FINDINGS

The data regarding visceral protein levels were examined in relation to nutritional supplementation, and compared with other nutritional parameters and clinical outcomes. Transthyretin and retinol-binding protein levels seem to be the most sensitive to nutritional intervention. They are also the earliest to rise at the decrease of acute-phase protein levels, therefore representing a good index of the reversing reprioritization of hepatic protein synthesis. An inconsistent relationship was found between visceral protein plasma levels and clinical outcome in intensive care unit patients, probably because of the difficulty in demonstrating clearly a beneficial effect of nutritional supplementation in highly catabolic conditions.

SUMMARY

In the acute stage of critical illness, the bi-weekly measurement of transthyretin together with acute-phase response protein plasma levels seems to be a 'window' on the metabolic condition (anabolism versus catabolism). However, only in the presence of stable inflammatory parameters do transthyretin levels reflect the adequacy of nutritional coverage.