This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Krassas, G. E. Articles by Flyvbjerg, A. Search for Related Content PubMed PubMed Citation Articles by Krassas, G. E. Articles by Flyvbjerg, A.

Free and Total Insulin-Like Growth Factor (IGF)-I, -II, and IGF Binding Protein-1, -2, and -3 Serum Levels in Patients with Active Thyroid Eye Disease

Department of Endocrinology and Metabolism (G.E.K., N.P., T.K.), Panagia General Hospital, 55132 Thessaloniki, Greece; Hippokrates (A.D.), Nuclear Medicine Center, 54622 Thessaloniki, Greece; and Medical Research Laboratories (J.F., J.W.C., A.F.), Aarhus Kommunehospital, University Hospital in Aarhus, DK-8000 Aarhus Center, Denmark

Address all correspondence and requests for reprints to: Prof. G. E. Krassas, M.D., Associate Professor of Medicine, Chairman, Department of Endocrinology, and Metabolism, Panagia Hospital, Tsimiski 92, 546 22 Thessaloniki, Greece. E-mail: krassas{at}the.forthnet.gr.

	Abstract

Top Abstract Introduction Patients and Methods Results Discussion References

 
To determine whether serum levels of total (T) and free (F) IGF-I and -II and IGF binding protein (IGFBP),-1, -2, and -3 are normal in euthyroid patients with Graves’ disease and active thyroid ophthalmopathy, we investigated the above-mentioned parameters in 21 patients (11 male, 10 female) aged 50.8 ± 11.8 yr (range 35–70) and 19 healthy individuals matched for age, gender, and body mass index. All patients had active thyroid eye disease (TED) with clinical activity scores 4 and positive orbital octreoscan in both eyes. Serum T and F IGF-I and IGF-II were determined using noncompetitive time-resolved monoclonal immunofluorometric assays, IGFBP-1 was determined by an in-house RIA, IGFBP-2 by a novel in-house time-resolved immunofluorometric assay, whereas IGFBP-3 by an immunoradiometric assay. All data are expressed as mean ± SD. Our results show that T and F IGF-I, -II, and IGFBP-1, -2, and -3 levels in patients were similar to controls and did not show any significant difference. Specifically, mean T IGF-I for patients group was 131 (61), F IGF-I was 0.47 (0.16), T IGF-II was 1056 (300), F IGF-II was 1.45 (0.54), IGFBP-1 was 33 (14), IGFBP-2 was 848 (377), and finally IGFBP-3 was 3953 (1422). For controls, mean T IGF-I was 146 (51), F IGF-I was 0.85 (0.43), T IGF-II was 939 (197), F IGF-II was 1.53 (0.53), IGFBP-1 was 44 (24), IGFBP-2 was 764 (316) and finally IGFBP-3 was 3721 (1017). Furthermore, no statistically differences emerged in the ratio between molar weights of T IGF-I/IGFBP-3 and T IGF-II/IGFBP-3, as well as to the F/T IGF-I and F/T IGF-II. Finally, no relationship was found between the levels of the above-mentioned parameters and clinical activity scores, octreoscan scores, and thyroid hormones. Our data demonstrate for the first time that serum levels of IGFs (including free fractions) and IGFBPs are not increased in euthyroid Graves’ patients with active TED. The increased IGF levels in retrobulbar tissues previously described, appear to be independent of serum IGFs concentration and probably represent autocrine and/or paracrine activity.

	Introduction

Top Abstract Introduction Patients and Methods Results Discussion References

 
THYROID EYE DISEASE (TED) is an inflammatory condition of the orbits and the commonest extrathyroidal complication of Graves’ disease (1, 2). It may precede, coincide with, or follow the onset of hyperthyroidism (3, 4, 5, 6, 7). TED is an organ-specific autoimmune disease characterized by enlargement of the extraocular muscles and expansion of retrobulbar fatty/connective tissue compartment. These changes cause exophthalmos, periorbital swelling and venous congestion, which are the principal clinical manifestations of the disease. Involvement of orbital soft tissues, cornea, and optic nerves may occur during the natural history of the disease (8).

The pathogenesis of TED is almost certainly multifactorial. Several cytokines (9, 10), including IGF-I (11, 12), have been implicated in the evolution of the orbital tissue changes in TED (10). The final step in the pathogenesis of TED is thought to be excessive production of glycosaminoglycans and collagen by orbital fibroblasts and preadipocytes (3). In vitro, IGF-I stimulates the secretion of collagen and glycosaminoglycans by orbital fibroblasts (13, 14, 15). Elevated serum levels of IGF-I are consistently present in patients with hyperthyroidism due to Graves’ disease (16). Furthermore, increased IGF-I immunoreactivity has been demonstrated in orbital tissues of a patient with TED (11). A role for IGF-I is therefore likely in the pathogenesis of TED. Moreover, recent studies have shown that therapy with octreotide is successful in some patients with active TED (17, 18, 19, 20), and somatostatin receptors have been demonstrated in the orbits of patients with TED both by scintigraphy (18) and immunostaining (21). However, the exact mechanism of action of somatostatin receptor agonists has not yet been elucidated (22). One possible explanation is suppression of IGF-I activity (22, 23). Serum levels of total and free IGFs, as well as IGF binding proteins (IGFBPs), have never been reported in euthyroid patients with active TED.

The present study was undertaken to determine whether serum levels of total and free IGF-I and II and IGFBP-1, -2, and -3 are abnormal in euthyroid patients with Graves’ disease and active thyroid ophthalmopathy.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Discussion References

 
Twenty-one euthyroid patients with Graves’ disease (11 male, 10 female) aged 50.8 ± 11.8 yr (range 35–70) receiving methimazole therapy (either alone or with thyroxine) for at least 3 months, were evaluated. Euthyroidism was defined as normal values of T₄ (75–135 nmol/liter) and T₃ (1.1–3.0 nmol/liter), with normal or suppressed serum TSH concentration (TSH: 4.0 mU/liter). T₃, T₄, and TSH were measured by RIA, as previously described (18). All patients had active thyroid ophthalmopathy, with clinical activity scores (CAS) 4 and positive orbital octreoscan in both eyes (Table 1).

Four patients were current smokers, 8 ex-smokers, whereas the remaining 9 were never smoked. Eight out of 19 controls were smokers, and 3 were ex-smokers (Table 1). In all patients and controls, serum levels of total and free IGF-I and -II and IGFBP-1, -2, and -3 were measured at 0900 h after an overnight fast

Radiopharmaceutical

The somatostatin derivative (DTPA-D-Phe1)-octreotide prepared by Mallinkrodt Diagnostica (Petten, Holland) was labeled with 244 MBq (6.6 mCi) ¹¹¹In and injected iv. The scintigraphic protocol and quantitation method have been reported in detail elsewhere (18, 19, 22, 24). Briefly, a previously described stereotaxic technique for slice selection was adopted (25). The transaxial images were standardized to yield a constant number of 16 slices (12 mm thick per slice) for all single photon emission computed tomography studies. Using a mid-line sagittal slice for better localization of the orbital area, five transaxial slices were chosen for quantitation, covering all the orbital and periorbital area.

Semiquantitative analysis. Somatostatin (SM) receptor binding was measured semiquantitatively by calculating for each subject both at the 4-h and 24-h acquisition the orbital-to-skull counts ratio in all the ten slices at both the 4-h and 24-h acquisition. All ratios were expressed as mean pixel count ratios for the two phases of the examination.

CAS

A disease activity score was calculated by assigning one point for the presence of each of the following signs and symptoms: spontaneous retrobulbar pain, pain on eye movements, eyelid erythema, conjunctival injection, chemosis, swelling of the caruncle, and eyelid edema or fullness. The sum of these points (range 0–7) defines the CAS (26).

Total and free IGF-I and -II

Serum total IGF-I and IGF-II were determined after acid-ethanol extraction using noncompetitive time-resolved monoclonal immunofluorometric assays as previously described (27). All samples were measured in one batch. The within and in-between assay coefficients of variation (CV) for this assay are less than 5% and 10%, respectively. Serum-free IGF-I and IGF-II were determined using ultrafiltration by centrifugation as previously described (28). Amicon YMT 30 membranes and Micropartition System-1 supporting devices were used (Amicon Division, Beverly, MA). Before centrifugation, serum samples were diluted (1 in 11) in Krebs-Ringer bicarbonate buffer (pH 7.4) containing 50 g/liter human serum albumin (Behring AG, Marburg, Germany). From each dilution, triplicates of 600 µl were applied to the membranes and incubated (30 min at 37 C) and centrifuged (1500 rpm at 37 C; model Rotixa/RP; Hettich Zentrifugen, Tuttlingen, Germany). The lower detection limit of free IGF-I and -II in the ultrafiltrates was 20 and 90 ng/liter, respectively. Including ultrafiltration and immunoassay, the within assays of CV averaged 18% and 12% for free IGF-I and -II, respectively.

IGFBP-1, IGFBP-2, and IGFBP-3 assays

IGFBP-1 was determined by an in-house RIA performed as described by Westwood et al. (29) with modifications. In brief, breakable Maxisorb microtiter plates (Nunc, Roskilde, Denmark) were coated with a polyclonal donkey antimouse IgG (4 mg/liter, 200 µl per well) (Sigma-Aldrich, Copenhagen, Denmark) dissolved in sodium-carbonate buffer (pH 9.6). After an overnight incubation at 5 C, all wells were washed once using a 50 mM Tris-HCl buffer (pH 8.0) added 0.9% (wt/vol) NaCl, 0.5% (vol/vol) Tween 20, and 0.05% (wt/vol) NaN₃ and blocked with 300 µl per well phosphate buffer (40 mmol/liter, pH 8.0) added 1% BSA (Sigma-Aldrich), 0.05% (wt/vol) NaN₃ and 0.6% (wt/vol) NaCl. After 2 h of blocking at room temperature, the wells were washed twice and 100 µl antigen [a serial dilution of recombinant human (rh) IGFBP-1 from HyTest (Turku, Finland) or diluted serum (1 in 4)] were added. All antigens were dissolved in assay buffer [40 mM phosphate buffer (pH 8.0), 0.2% (wt/vol) BSA, 0.05% (wt/vol) NaN₃, 0.9% (wt/vol) NaCl and 2% (vol/vol) Tween 20)]. In addition, 50 µl of ¹²⁵I-labeled rh-IGFBP-1 (10.000 cpm per well) and 50 µl of a monoclonal IGFBP-1 antibody, which recognizes all human phosphoforms of IGFBP-1 (MAB 6303 from Medix Biochemica, Kauniainen, Finland) were added. Both latter reagents were dissolved in assay buffer. All samples (standards, diluted serum samples and nonspecific binding) were analyzed in duplicate. The plates were incubated for 2 d at 5 C, washed three times, and the breakable wells counted for 3 min in a gamma counter. The lower detection limit was estimated to approximately 2.5 µg/liter, the half-maximal displacement occurred at 25 µg/liter, and the upper IGFBP-1 standard was 200 µg/liter. The with-in and in-between assay CV averaged less than 5% and 16%, respectively. Addition of rhIGF-I and -II (Austral Biologicals, San Ramon, CA), and rhIGFBP-2, -3, -4, and -5 (from R&D Systems, Abingdon, UK) up to 10,000 µg/liter did not affect the measured concentration of IGFBP-1 to any significant degree.

IGFBP-2 was determined by a novel in-house time-resolved immuno-fluorometric assay based on reagents from R&D Systems (Abingdon, UK). Microtiter test-plates (Nunc) were coated with a monoclonal human IGFBP-2 antibody (2.0 mg/liter, 200 µl per well) dissolved in sodium-carbonate buffer (pH 9.6), and incubated overnight at 37 C. On the following day, plates were washed once and blocked for 2 h at room temperature with 300 µl phosphate buffer (40 mmol/liter, pH 8.0) containing 1% (wt/vol) BSA, 0.05% (wt/vol) NaN₃, 0.9% (wt/vol) NaCl, and 1.6 g/liter Titriplex V. After blocking, all wells were washed and 25 µl of standard or unknown samples were added and 175 µl biotinylated polyclonal goat antibody (250 µg/liter) raised against human IGFBP-2. All antigens were diluted in an in-house assay buffer made of 40 mmol/liter phosphate (pH 8.0), 0.2% (wt/vol) human serum albumin (Behring AG), 0.9 (wt/vol) NaCl, 2% (vol/vol) Tween 20, 1.6 g/liter Titriplex V, and 0.05% (wt/vol) NaN₃. IGFBP-2 standards were made by serial dilution, ranging from 1–500 µg/liter. Unknown samples were diluted 1 in 10 in assay buffer before assay. All standards and unknown samples were assayed in duplicate whereas nonspecific binding was assayed in quadruplicate. The IGFBP-2 standard curve was linear from 1–500 µg/liter. The signal to noise ratio of the lowest standard averaged 2.5, within and in-between assay CV 5% and 12%, respectively. Addition of serial dilutions of rhIGF-I or -II ranging from 10–10,000 µg/liter did not change the signal, and the cross-reactivity of serial dilutions of rhIGFBP-1, -3, -4, and -5 up to 10,000 µg/liter was estimated to less than 0.1%.

Serum IGFBP-3 was measured by an immunoradiometric assay (Diagnostic System Laboratories Inc., Webster, TX). The within and in-between assay CV for this assay are less than 5% and 10%, respectively.

Statistical analysis

All data are expressed as mean ± SD. Normal distribution of all parameters was tested by the Kolmogorov-Smirnov test. Statistical analysis was performed by unpaired two-tailed Student’s t test and regression analysis. Two-sided P < 0.05 was considered significant.

	Results

Top Abstract Introduction Patients and Methods Results Discussion References

 
Our results are presented in Table 2. As shown in this table, total IGF-I and -II and free IGF-I, -II, IGFBP-1, -2, and -3 levels in patients were similar to controls and did not show any significant difference. Furthermore, no statistically significant differences emerged in the molar ratio between total IGF-I and -II and IGFBP-3 as well as in the ratio of free to total IGF-I and free to total IGF-II. Mean CAS was 5.3 ± 1.01, whereas the mean octreoscan score was 1.82 ± 0.12. Finally, no relationship was found between the levels of the above-mentioned parameters and CAS, octreoscan scores and thyroid hormones.

	Discussion

Top Abstract Introduction Patients and Methods Results Discussion References

In 1986, Hansson et al. (11) demonstrated for the first time that IGF-I levels were increased in samples of eye muscle and fat, which were received after a decompression surgery from two patients with active thyroid eye disease. They suggested that the increase in orbital IGF-I concentration may be a crucial factor for the marked hypertrophy of the ocular muscles and connective tissue. In 1989, Hansson (30) also demonstrated in biopsy specimens from retrobulbar tissue from 6 patients with malignant exophthalmos, intense IGF-I-like immunoreactivity at medial rectus muscle cells, fat cells, and retrobulbar inflammatory cells. They proposed that the local high IGF-I formation is induced by the inflammatory process and exerts its effects in an autocrine and/or paracrine manner.

In 1998, Maiorano et al. (31) investigated the expression of IGF-I and its corresponding receptor, by means of immunohistochemistry, in the surgical specimens obtained from 6 patients with Graves’ disease. Moreover, IGF-I mRNA expression was analyzed in one such case by means of Northern hybridization. They suggested that IGF-I and IGF-I receptor may be actively involved in the pathogenesis of Graves’ disease, whereas their mechanism of action should be different (paracrine vs. autocrine).

Finally, Pasquali et al. (21) recently investigated the expression of SM and SM receptor genes in primary cultures of fibroblasts established from retroorbital tissue of TED patients and of control subjects. They also determined SM-specific binding sites by competitive binding of [¹²⁵ITyr (11)]SST-14 and the effect of octreotide on cell growth, cAMP accumulation, Bcl-2 intracellular levels, and apoptosis in TED fibroblast primary cultures. They concluded that SM and SM transcripts are expressed and functional in cultured retroorbital fibroblasts. Moreover, they suggested that the presence of class 1 SM in TED tissue and the inhibition exerted by octreotide on retroorbital cell growth and activity in vitro may account for the effects of SM analogs (SM-a) administration in vivo in TED (21).

It is well known that IGF-I circulates, bound to several binding proteins that prolong the plasma half-life of IGF-I and modulate its bioavailability and action. The IGFBPs are differentially regulated. IGFBP-3, the predominant plasma binding protein, is regulated slowly and in parallel with serum GH concentrations (32).

So far, no study has been published providing data on serum levels of IGFs and IGFBPs in such patients, although IGF-I levels are implicated in the possible mechanism of action of SM-a in this disease (22, 23).

Chang et al. (17) in a reply letter to B.M.J. stated that the IGF-I concentration in serum was not raised in such patients. However, those were and still are unpublished data (personal communication).

Prummel et al. (33) investigated the effect of long-term prednisone treatment on GH and IGF-I levels in 18 euthyroid patients with Graves’ opthalmopathy and found that baseline serum IGF-I levels were within normal range.

In addition, Khoo et al. (34) reported that IGF-I levels fell in 8 patients with Graves’ opthalmopathy after treating them with SM-a. However, no information was given, concerning the method used for measuring IGF-I. Furthermore, that study was uncontrolled.

Our data demonstrate for the first time that IGFs (including free fractions) and IGFBPs are not increased in euthyroid Graves’ patients with active thyroid eye disease. The increased IGF levels in retrobulbar tissues previously described (11), appear to be independent of serum IGFs concentration and probably represent autocrine and/or paracrine activity. SM-a have been shown to have a beneficial effect in patients with TED. One possible mechanism of SM-a action is suppression of IGF-I levels. On the basis of our results, it can be assumed that IGF-I may be produced locally in orbital tissues, rather than derived from serum, and one possible mechanism of action of SM-a should be a reduction of IGF-I synthesis in the retrobulbar tissues. However, further studies are needed to examine retrobulbar IGF-I-like immunoreactivity before and after administration of somatostatin, as well as IGFs and IGFBPs levels after treatment with SM-a in patients with active TED.

	Acknowledgments

 
We acknowledge Dr. Petros Perros, Consultant Physician and Endocrinologist at Freeman Hospital (Newcastle UK), for his valuable comments and suggestions; and also Miss Gialantzi Anna, Kirsten Nyborg, Joan Hansen, and Susanne Sorensen for their excellent secretariat and technical assistance.

	Footnotes

 
Abbreviations: CAS, Clinical activity scores; CV, coefficient of variation; F, free; IGFBP, IGF binding protein; rh, recombinant human; SM, somatostatin; SM-a, SM analogs; T, total; TED, thyroid eye disease.

Received August 21, 2002.

Accepted September 24, 2002.

	References

Top Abstract Introduction Patients and Methods Results Discussion References

 

1. Jacobson DH, Gorman CA 1984 Endocrine ophthalmopathy: current ideas concerning etiology, pathogenesis and treatment. Endocr Rev 5:200–220[Medline]
2. Burch HB, Wartofsky L 1993 Graves’ ophthalmopathy: current concepts regarding pathogenesis and management. Endocr Rev 14:747–793[Abstract]
3. Bartalena L, Pinchera A, Marcocci C 2000 Management of Graves’ ophthalmopathy: reality and perspectives. Endocr Rev 21:168–199[Abstract/Free Full Text]
4. Weetman A 2000 Medical progress: Graves’ disease. N Engl J Med 343:1236–1248[Free Full Text]
5. Wiersinga WM 1997 Graves’ ophthalmopathy. Thyroid Int 3:3–15
6. Perros P, Kendall-Taylor P 1998 Natural history of thyroid eye disease. Thyroid 8:423–425[Medline]
7. Kendall-Taylor P, Perros P 1998 Clinical presentation of thyroid-associated orbitopathy. Thyroid 8:427–428[Medline]
8. Bahn RS, Heufelder AE 1993 Pathogenesis of Graves’ ophthalmopathy. N Engl J Med 329:1468–1475[Free Full Text]
9. Natt N, Bahn RS 1997 Cytokines in the evolution of Graves’ ophthalmopathy. Autoimmunity 26:129–136[Medline]
10. Bahn RS 1998 Cytokines in thyroid eye disease: potential for anti-cytokine therapy. Thyroid 8:415–418[Medline]
11. Hansson HA, Petruson B, Skottner A 1986 Somatomedin C in the pathogenesis of malignant exophthalmos of endocrine origin. Lancet 1:218–219[Medline]
12. Weightman DR, Perros P, Sherif IH, Kendall-Taylor P 1993 Autoantibodies to IGF-I binding sites in thyroid associated ophthalmopathy. Autoimmunity 16:251–257[Medline]
13. Imai Y, Odajima R, Inoue Y, Shishiba Y 1992 Effect of growth factors on hyaluronan and proteoglycan synthesis by retroocular tissue fibroblasts of Graves’ ophthalmopathy in culture. Acta Endocrinol (Copenh) 126:541–552
14. Heufelder AE 1995 Pathogenesis of Graves’ ophthalmopathy: recent controversies and progress. Eur J Endocrinol 132:532–541[Medline]
15. Heufelder AE 1997 Somatostatin analogues in Graves’ ophthalmopathy. J Endocrinol Invest 20 (Suppl 7):50–52
16. Lakatos P, Foldes J, Nagy Z, Takacs I, Speer G, Horvath C, Mohan S, Baylink DJ, Stern PH 2000 Serum insulin-like growth factor-I, insulin-like growth factor binding proteins, and bone mineral content in hyperthyroidism. Thyroid 10:417–423[Medline]
17. Chang TC, Kao SCS, Huang KM 1992 Octreotide and Graves’ ophthalmopathy and pretibial myxoedema. Br Med J 304:158
18. Krassas GE, Dumas A, Pontikides N, Kaltsas Th 1995 Somatostatin receptor scintigraphy and octreotide treatment in patients with thyroid eye disease. Clin Endocrinol (Oxf) 42:571–580[Medline]
19. Krassas GE, Kaltsas Th, Dumas A, Pontikides N, Tolis G 1997 Lanreotide in the treatment of patients with thyroid eye disease. Eur J Endocrinol 136:416–422[Abstract]
20. Uysal AR, Corapcioglu D, Tonyukuk VC, Gullu S, Sav H, Kamel N, Erdogan G 1999 Effect of octreotide treatment on Graves’ ophthalmopathy. Endocr J 46:573–577[Medline]
21. Pasquali D, Vassallo P, Esposito D, Bonavolonta G, Bellastella A, Sinisi AA 2000 Somatostatin receptor gene expression and inhibitory effects of octreotide on primary cultures of orbital fibroblasts from Graves’ ophthalmopathy. J Mol Endocrinol 25:63–71[Abstract]
22. Krassas GE 1998 Somatostatin analogues in the treatment of thyroid eye disease. Thyroid 8:443–445[Medline]
23. Krassas GE, Heufelder AE 2001 Immunosuppressive therapy in patients with thyroid eye disease: an overview of current concepts. Eur J Endocrinol 144:311–318[Abstract]
24. Krassas GE, Kahaly GJ 1999 The role of octreoscan in thyroid eye disease. Eur J Endocrinol 140:373–375[Abstract]
25. Ichise M, Toaym H, Vines DC, Chung DG, Kirsch JC 1992 Neuroanatomical localization for clinical SPECT perfusion brain imaging: a practical proportional grid method. Nucl Med Commun 13:861–866[Medline]
26. Anonymous. 1992 Thyroid 2:235–236[Medline]
27. Frystyk J, Dinesen B, Orskov H 1995 Non-competitive time-resolved immunofluorometric assays for determination of human insulin-like growth factor I and II. Growth Reg 5:169–176[Medline]
28. Frystyk J, Skjærbæk C, Dinesen B, Orskov H 1994 Free insulin-like growth factors (IGF-I and IGF-II) in human serum. FEBS Lett 348:185–191[CrossRef][Medline]
29. Westwood M, Gibson JM, Davies AJ, Young RJ, White A 1994 The phosphorylation pattern of insulin-like growth factor-binding protein-1 in normal plasma is different from that in amniotic fluid and changes during pregnancy. J Clin Endocrinol Metab 79:1735–1741[Abstract]
30. Hansson HA 1989 Aspects on growth factors in exophthalmos Acta Endocrinol (Copenh) 21(Suppl 2):107–111
31. Maiorano E, Perlino E, Triggiani VV, Nacchiero M, Giove E, Ciampolillo A 1998 Insulin-like growth factor-1 and insulin-like growth factor receptor in thyroid tissues of patients with Graves’ disease. Int J Mol Med 2:483–486[Medline]
32. Hartman ML 1996 Physiological regulators of growth hormone secretion. In: Juul A, Jorgensen OL, eds Growth hormone in adults. Physiological and clinical aspects. Cambridge: Cambridge University Press; 5–35
33. Prummel MF, Wiersinga WM, Oosting H, Endert E 1996 The effect of long-term prednisone on growth hormone and insulin-like growth factor-I. J Endocrinol Invest 19:620–623[Medline]
34. Khoo DHC, Tan YT, Fok ACK, Tan CE 1995 Octreotide in the management of Graves’ ophthalmopathy—changes in insulin-like growth factor 1 levels do not predict clinical response. Am J Clin Res 4:33–42

This article has been cited by other articles:

				M. Hansen, S. O. Koskinen, S. G. Petersen, S. Doessing, J. Frystyk, A. Flyvbjerg, E. Westh, S. P. Magnusson, M. Kjaer, and H. Langberg Ethinyl oestradiol administration in women suppresses synthesis of collagen in tendon in response to exercise J. Physiol., June 15, 2008; 586(12): 3005 - 3016. [Abstract] [Full Text] [PDF]

				R. K. Stoving, J.-W. Chen, D. Glintborg, K. Brixen, A. Flyvbjerg, K. Horder, and J. Frystyk Bioactive Insulin-Like Growth Factor (IGF) I and IGF-Binding Protein-1 in Anorexia Nervosa J. Clin. Endocrinol. Metab., June 1, 2007; 92(6): 2323 - 2329. [Abstract] [Full Text] [PDF]

				A. A. Samani, S. Yakar, D. LeRoith, and P. Brodt The Role of the IGF System in Cancer Growth and Metastasis: Overview and Recent Insights Endocr. Rev., February 1, 2007; 28(1): 20 - 47. [Abstract] [Full Text] [PDF]

				J.-W. Chen, M. F Nielsen, A. Caumo, H. Vilstrup, J. S. Christiansen, and J. Frystyk Changes in bioactive IGF-I and IGF-binding protein-1 during an oral glucose tolerance test in patients with liver cirrhosis. Eur. J. Endocrinol., August 1, 2006; 155(2): 285 - 292. [Abstract] [Full Text] [PDF]

				H. Zhang, D. Chung, Y.-C. Yang, L. Neely, S. Tsurumoto, J. Fan, L. Zhang, M. Biamonte, J. Brekken, K. Lundgren, et al. Identification of new biomarkers for clinical trials of Hsp90 inhibitors Mol. Cancer Ther., May 1, 2006; 5(5): 1256 - 1264. [Abstract] [Full Text] [PDF]

				U. Espelund, J. M. Bruun, B. Richelsen, A. Flyvbjerg, and J. Frystyk Pro- and mature IGF-II during diet-induced weight loss in obese subjects Eur. J. Endocrinol., December 1, 2005; 153(6): 861 - 869. [Abstract] [Full Text] [PDF]

				K. Stokes, M. Nevill, J. Frystyk, H. Lakomy, and G. Hall Human growth hormone responses to repeated bouts of sprint exercise with different recovery periods between bouts J Appl Physiol, October 1, 2005; 99(4): 1254 - 1261. [Abstract] [Full Text] [PDF]

				D. Glintborg, R. K. Stoving, C. Hagen, A. P. Hermann, J. Frystyk, J. D. Veldhuis, A. Flyvbjerg, and M. Andersen Pioglitazone Treatment Increases Spontaneous Growth Hormone (GH) Secretion and Stimulated GH Levels in Polycystic Ovary Syndrome J. Clin. Endocrinol. Metab., October 1, 2005; 90(10): 5605 - 5612. [Abstract] [Full Text] [PDF]

				J. D. Veldhuis, J. Frystyk, A. Iranmanesh, and H. Orskov Testosterone and Estradiol Regulate Free Insulin-Like Growth Factor I (IGF-I), IGF Binding Protein 1 (IGFBP-1), and Dimeric IGF-I/IGFBP-1 Concentrations J. Clin. Endocrinol. Metab., May 1, 2005; 90(5): 2941 - 2947. [Abstract] [Full Text] [PDF]

				J. L. Wemeau, P. Caron, A. Beckers, V. Rohmer, J. Orgiazzi, F. Borson-Chazot, M. Nocaudie, P. Perimenis, S. Bisot-Locard, I. Bourdeix, et al. Octreotide (Long-Acting Release Formulation) Treatment in Patients with Graves' Orbitopathy: Clinical Results of a Four-Month, Randomized, Placebo-Controlled, Double-Blind Study J. Clin. Endocrinol. Metab., February 1, 2005; 90(2): 841 - 848. [Abstract] [Full Text] [PDF]

				J.-W. Chen, K. Hojlund, H. Beck-Nielsen, J. Sandahl Christiansen, H. Orskov, and J. Frystyk Free Rather than Total Circulating Insulin-Like Growth Factor-I Determines the Feedback on Growth Hormone Release in Normal Subjects J. Clin. Endocrinol. Metab., January 1, 2005; 90(1): 366 - 371. [Abstract] [Full Text] [PDF]

				A. J. Dickinson, B. Vaidya, M. Miller, A. Coulthard, P. Perros, E. Baister, C. D. Andrews, L. Hesse, J. T. Heverhagen, A. E. Heufelder, et al. Double-Blind, Placebo-Controlled Trial of Octreotide Long-Acting Repeatable (LAR) in Thyroid-Associated Ophthalmopathy J. Clin. Endocrinol. Metab., December 1, 2004; 89(12): 5910 - 5915. [Abstract] [Full Text] [PDF]

				C. A. Hedman, J. Frystyk, T. Lindstrom, J.-W. Chen, A. Flyvbjerg, H. Orskov, and H. J Arnqvist Residual {beta}-Cell Function More than Glycemic Control Determines Abnormalities of the Insulin-Like Growth Factor System in Type 1 Diabetes J. Clin. Endocrinol. Metab., December 1, 2004; 89(12): 6305 - 6309. [Abstract] [Full Text] [PDF]

				D. Zhang, M. Bar-Eli, S. Meloche, and P. Brodt Dual Regulation of MMP-2 Expression by the Type 1 Insulin-like Growth Factor Receptor: THE PHOSPHATIDYLINOSITOL 3-KINASE/Akt AND Raf/ERK PATHWAYS TRANSMIT OPPOSING SIGNALS J. Biol. Chem., May 7, 2004; 279(19): 19683 - 19690. [Abstract] [Full Text] [PDF]

				L. Duplomb, B. Chaigne-Delalande, P. Vusio, S. Raher, Y. Jacques, A. Godard, and F. Blanchard Soluble Mannose 6-Phosphate/Insulin-Like Growth Factor II (IGF-II) Receptor Inhibits Interleukin-6-Type Cytokine-Dependent Proliferation by Neutralization of IGF-II Endocrinology, December 1, 2003; 144(12): 5381 - 5389. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Krassas, G. E. Articles by Flyvbjerg, A. Search for Related Content PubMed PubMed Citation Articles by Krassas, G. E. Articles by Flyvbjerg, A.