IGF-I bioactivity might reflect different aspects of quality of life than total IGF-I in GH-deficient patients during GH treatment

The insulin-like growth factor-I receptor stimulating activity (IRSA) in health and disease

Determination of true IGF-I bioactivity in serum and other biological fluids is still a substantial challenge. The IGF-IR Kinase Receptor Activation assay (IGF-IR KIRA assay) is a novel tool to asses IGF-IR stimulating activity (IRSA) and has opened a new era in studying the IGF system. In this paper we discuss many studies showing that measuring IRSA by the IGF-IR KIRA assay often provides fundamentally different information about the IGF system than the commonly used total IGF-I immunoassays. With the IGF-IR KIRA assay phosphorylation of tyrosine residues of the IGF-IR is used as read out to quantify IRSA in unknown (serum) samples. The IGF-IR KIRA assay gives information about net overall effects of circulating IGF-I, IGF-II, IGFBPs and IGFBP-proteases on IGF-IR activation and seems especially superior to immunoreactive total IGF-I in monitoring therapeutic interventions. Although the IRSA as measured by the IGF-IR KIRA assay probably more closely reflects true bioactive IGF-I than measurements of total IGF-I in serum, the IGF-IR KIRA assay in its current form does not give information about all the post-receptor intracellular events mediated by the IGF-IR. Interestingly, in several conditions in health and disease IRSA measured by the IGF-IR KIRA assay is considerably higher in interstitial fluid and ascites than in serum. This suggests that both the paracrine (local) and endocrine (circulating) IRSA should be measured to get a complete picture about the role of the IGF system in health and disease.

Disagreement in normative IGF-I levels may lead to different clinical interpretations and GH dose adjustments in GH deficiency

INTRODUCTION AND BACKGROUND

Normative data for the iSYS IGF-I assay have been published both in the VARIETE cohort and by Bidlingmaier et al.

OBJECTIVE

To investigate whether normative data of the VARIETE cohort lead to differences in Z-scores for total IGF-I and clinical interpretation compared to normative data of Bidlingmaier et al.

DESIGN

We used total IGF-I values previously measured by the IDS-iSYS assay in 102 GH-deficient subjects before starting GH treatment and after 12 months of GH treatment. Z-scores were calculated for all samples by using the normative data of the VARIETE cohort and by the normative data reported by Bidlingmaier et al.

RESULT

Before GH treatment, Z-scores calculated by using the normative data of the VARIETE cohort were significantly lower than those calculated by the normative data of Bidlingmaier et al: -2.40 (-4.52 to +1.31) (mean [range]) vs. -1.41 (-3.14 to +1.76); P < .001). After 12 months of GH treatment, again the Z-scores based on the normative data of the VARIETE cohort were significantly lower than those based on the normative data of Bidlingmaier et al: -0.65 (-4.32 to +2.79) vs 0.21 (-3.00 to +3.28); P < .001).

CONCLUSION

IGF-I Z-scores in 102 GH-deficient subjects differed significantly when normative data from two different sources were used. In daily clinical practice, this would most likely have led to different clinical interpretations and GH dose adjustments.

Assessment of quality of life on 4-year growth hormone therapy in Japanese patients with adult growth hormone deficiency: A post-marketing, multicenter, observational study

OBJECTIVE

Improvement of quality of life (QOL) by growth hormone (GH) therapy was not demonstrated in Japanese adult growth hormone deficiency (AGHD) patients by either the QOL Assessment of Growth Hormone Deficiency in Adults or the Questions on Life Satisfaction-Hypopituitarism, which are widely used to evaluate QOL in Western AGHD patients. We therefore evaluated QOL in Japanese AGHD patients receiving recombinant GH, Norditropin® (Novo Nordisk A/S, Denmark), using the newly developed Adult Hypopituitarism Questionnaire (AHQ).

DESIGN

This multicenter, non-interventional, observational study in Japanese patients with severe AGHD was conducted from 1 October 2009 to 30 September 2014. Patients with severe AGHD already receiving somatropin and somatropin-naïve patients were included. GH therapy (Norditropin®) was initiated as injections of 0.021mg/kg/week divided into 6-7 doses/week, and was adjusted according to clinical responses. Demographic/clinical data were obtained from medical records or by patient recall. QOL was assessed using the AHQ at baseline; 3, 6, and 12months; and annually up to 4years.

RESULTS

Of 387 registered patients, 161 were eligible for QOL analysis. AHQ scores significantly improved after 3months of treatment. Improvements in the psycho-social and physical domains were statistically significant throughout the 4-year study period. Although the GH dose was increased in females such that insulin-like growth factor-1 levels reached those of males, QOL improvements in females did not reach those of males. Despite the greater GH dose in child-onset patients, limited QOL improvements were observed in child-onset vs adult-onset cases.

CONCLUSIONS

Four-year GH treatment in Japanese AGHD patients elicits sustained improvement in QOL as assessed by AHQ scores.

Changes in circulating IGF1 receptor stimulating activity do not parallel changes in total IGF1 during GH treatment of GH-deficient adults

CONTEXT

Previously we demonstrated that IGF1 receptor stimulating activity (IGF1RSA) offers advantages in diagnostic evaluation of adult GH deficiency (GHD). It is unknown whether IGF1RSA can be used to monitor GH therapy.

OBJECTIVE

To investigate the value of circulating IGF1RSA for monitoring GH therapy.

DESIGN/METHODS

106 patients (54 m; 52 f) diagnosed with GHD were included; 22 were GH-naïve, 84 were already on GH treatment and discontinued therapy 4 weeks before baseline values were established. IGF1RSA was determined by the IGF1R kinase receptor activating assay, total IGF1 by immunoassay (Immulite). GH doses were titrated to achieve total IGF1 levels within the normal range.

RESULTS

After 12 months, total IGF1 and IGF1RSA increased significantly (total IGF1 from 8.1 (95% CI 7.3-8.9) to 14.9 (95% CI 13.5-16.4) nmol/l and IGF1RSA from 115 (95% CI 104-127) to 181 (95% CI 162-202) pmol/l). After 12 months, total IGF1 normalized in 81% of patients, IGF1RSA in 51% and remained below normal in more than 40% of patients in whom total IGF1 had normalized.

CONCLUSIONS

During 12 months of GH treatment, changes in IGF1RSA did not parallel changes in total IGF1. Despite normalization of total IGF1, IGF1RSA remained subnormal in a considerable proportion of patients. At present our results have no short-term consequences for GH therapy of GHD patients. However, based on our findings we propose future studies to examine whether titrating GH dose against IGF1RSA results in a better clinical outcome than titrating against total IGF1.

Quality of life in patients with hypopituitarism

PURPOSE OF REVIEW

Quality of life (QoL) is impaired in patients with adults with growth hormone deficiency (AGHD) of any cause, especially if additional hypopituitarism is present, and improves after replacement therapy with recombinant human growth hormone (rhGH). This review includes relevant publications since 2013.

RECENT FINDINGS

Recent findings confirm that most patients with AGHD who improve their QoL after rhGH therapy experience persistent effects for years, if replacement therapy is maintained. Sometimes, however, QoL may not normalize completely, especially if it is caused by a craniopharyngioma (because of concomitant neuropsychological comorbidities that affect autonomy and cognitive function), or functional pituitary tumours, i.e., in Cushing's disease, in which chronic brain exposure to hypercortisolism is associated with more depression, anxiety, loss of memory and emotional distress. Another group in which QoL and energy rarely normalize despite improving after rhGH is hypopituitarism because of traumatic brain injury. Worse QoL is seen in patients who also suffer insomnia, depression, negative illness perceptions and are treated in a rural (compared with an urban) healthcare environment. Better QoL after rhGH is seen in AGHD patients who are not depressed, after successful surgery, living in Europe (rather than the USA), with poorer baseline QoL scores, less obesity and no impaired vision.

SUMMARY

Further improvement of QoL may be possible with individualized psychosocial interventions.

In active acromegaly, IGF1 bioactivity is related to soluble Klotho levels and quality of life

The value of measuring IGF1 bioactivity in active acromegaly is unknown. Soluble Klotho (S-Klotho) level is elevated in active acromegaly and it has been suggested that S-Klotho can inhibit activation of the IGF1 receptor (IGF1R). A cross-sectional study was carried out in 15 patients with active acromegaly based on clinical presentation, unsuppressed GH during an oral glucose tolerance test, and elevated total IGF1 levels (>+2 s.d.). Total IGF1 was measured by immunoassay, IGF1 bioactivity by the IGF1R kinase receptor activation assay and S-Klotho by an ELISA. Quality of Life (QoL) was assessed by Acromegaly QoL (AcroQoL) Questionnaire and Short-Form-36 Health Survey Questionnaire (SF-36). Out of 15 patients, nine had IGF1 bioactivity values within the reference range. S-Klotho was higher in active acromegaly compared with controls. Age-adjusted S-Klotho was significantly related to IGF1 bioactivity (r=0.75, P=0.002) and to total IGF1 (r=0.62, P=0.02). IGF1 bioactivity and total IGF1 were inversely related to the physical component summary of the SF-36 (r=-0.78, P=0.002 vs r=-0.60, P=0.03). Moreover, IGF1 bioactivity, but not total IGF1, was significantly inversely related to the physical dimension of the AcroQoL Questionnaire (r=-0.60, P=0.02 vs r=-0.37, P=0.19). In contrast to total IGF1, IGF1 bioactivity was within the reference range in a considerable number of subjects with active acromegaly. Elevated S-Klotho levels may have reduced IGF1 bioactivity. Moreover, IGF1 bioactivity was more strongly related to physical measures of QoL than total IGF1, suggesting that IGF1 bioactivity may better reflect physical limitations perceived in active acromegaly.

Extensive expertise in endocrinology: UK stance on adult GH replacement: the economist vs the endocrinologist

In the UK, through the use of a forced economic model, endocrinologists are in the curious position of offering GH replacement to some patients with severe GH deficiency (GHD) but withholding it from other patients with even more severe GHD. This approach is counter-intuitive to endocrine practice in treating endocrine deficiency states. For all other endocrine deficiencies, one would opt for treating those with the most severe biochemical evidence of deficiency first. If this endocrine approach was applied to adult GH replacement in an era of rationing, one would start with the GHD patients with a pathologically low IGF1 level. Given that the prevalence of subnormal IGF1 levels in a GHD population is age-dependent, this would result in GH replacement being offered to more young adult onset (AO) GHD and childhood onset GHD adults, and less often to middle-aged and elderly AO GHD adults. This in itself has the added advantage that the skeletal benefits appear more real in the former cohort of patients.