Archives of Medical Research 40 (2009) 42e47

ORIGINAL ARTICLE

Insulin-like Growth Factor-I Gene and Insulin-like Growth Factor BindingProtein-3 Polymorphism in Patients with Thyroid Dysfunction

Raziye Kursunluoglu,a Sebahat Turgut,a Fulya Akin,b Mehmet Bastemir,c

Bunyamin Kaptanoglu,d Osman Genc,a and Gunfer Turguta

aDepartment of Physiology, bDepartment of Internal Medicine, Division of Endocrinology, Faculty of Medicine, University of Pamukkale, Denizli, TurkeycDepartment of Endocrinology, Sani Konukoglu Medical Center, Gaziantep, Turkey

dDepartment of Biochemistry, Faculty of Medicine, University of Pamukkale, Denizli, Turkey

Received for publication May 22, 2008; accepted September 22, 2008 (ARCMED-D-08-00222).

Address reprint re

sitesi Tıp Fakultesi

rkursunluoglu@pau.e

0188-4409/09 $eseedoi: 10.1016/j.arcm

Background and Aims. Thyroid hormones have important roles in normal growth andskeletal muscle development. IGF-I is one of the most important growth factors and isneeded for the proliferation and development of thyroid cells. It stimulates fibroblasts,follicular and endothelia cells in thyroid gland. It has been shown that thyroid hormonesplay an important role in the regulation of IGF-I and IGFBP-3. In this study we proposedthat IGF-I (CA)19 and IGFBP-3e202 A/C gene polymorphism may affect thyroidfunctions. For this purpose, frequency of IGF-I (CA)19 and IGFBP-3e202 A/C genepolymorphism in hypo- and hyperthyroid patients and possible role of these polymor-phism in thyroid functions were investigated.

Methods. This study was performed on 37 volunteer hyperthyroid and 76 hypothyroidpatients as well as with 50 healthy subjects as controls. DNA isolation was applied in periph-eral blood samples obtained from patients and controls. Required areas were amplified withPCR by using proper primers belonging to these gene areas from the isolated DNA samples.The products were evaluated with visualization by UV gel documentation system.

Results. Frequency of IGF-I (CA)19 gene polymorphism among hypothyroidism patients,hyperthyroidism patients and controls were statistically significant (c2 5 11.55, df 5 4,p 5 0.021). Genotypic variations between hyper- and hypothyroid patients were significant(c2 5 11.39, df 5 2, p 5 0.003), whereas there was no difference in IGF-I (CA)19 gene poly-morphism between the patients and controls. Differences in the IGFBP-3e202 A/C genepolymorphism between controls and hypo- as well as hyperthyroid patients were not signif-icant. But IGFBP-3e202 A/C gene polymorphism genotype frequencies showed a signifi-cant difference between hypo- and hyperthyroid patients (c2 5 6.24, df 5 2, p 5 0.044).

Conclusions. These findings suggests that IGF-I (CA)19 and IGFBP-3e202 A/C genepolymorphisms may be a risk factor for hypothyroidism. � 2009 IMSS. Published byElsevier Inc.

Key Words: Hypothyroidism, Hyperthyroidism, Insulin like growth factor-I (IGF-I), Insulin-like

growth factor binding protein-3 (IGFBP-3), Po lymorphism.

Introduction

Thyroid hormones are amino acid species synthesizedby follicular epithelium cells of thyroid gland and play

quests to: Raziye Kursunluoglu, Pamukkale Univer-

Fizyoloji A.D., Kınıklı/Denizli, Turkey; E-mail:

du.tr; raziye.kursunluoglu@mynet.com

front matter. Copyright � 2009 IMSS. Published by Elseved.2008.10.009

important roles in the growth and development of varioustissues (1). They also regulate overall metabolic activityand basal metabolism (2). Thyroid hormones have a vitalrole in normal growth and skeletal development. They stim-ulate the synthesis of tissue growth factors by inducingDNA and RNA synthesis. It has also been known that theyinduce growth hormone gene expression by directly affect-ing the pituitary gland (3).

ier Inc.

43Associations with Hyper- and Hypothyroidism of IGF-I and IGFBP-3

Insulin-like growth factors (IGF-I) are important hor-mones identified in 1978 and having various effects on differ-ent tissue and organs. Most IGF-I found in the circulation areproduced in liver and transported to other tissues, acting as anendocrine hormone. In addition, they are synthesized bymany tissues such as lung, kidney, skeletal muscle, heart,spleen, gastrointestinal system, ovaries and testes. IGF-Iplays a paracrine and autocrine hormone role (4). IGF-Iforms complexes with IGF-binding proteins (IGFBP) thatregulate free IGF levels in both circulation and tissues (5).This situation extends the half-life of IGF-I in circulation.All types of the binding proteins are present in plasma andIGF-binding protein-3 (IGFBP-3) is responsible for 95% ofbinding in circulation. IGF-I and IGFBP-3 have importantroles in the regulation of late fetal development. The bloodlevel of IGF-I increases during growth periods (6), pregnancy(7), exercise (8) and stress (9).

Thyroid hormones affect serum levels of IGF-I. It hasbeen known that thyroid hormones have important rolesin the regulation of IGF-I and IGFBP-3 activities. IGF-Iis synthesized and secreted by thyroid cells, and bothIGF-1 and IGFBP-3 have been shown to be related to thefunction and growth of the thyroid (10). IGF-I stimulates fi-broblasts, follicular cells and endothelial cells in the thyroidgland. Association between IGF-I and TSH is required forthe follicular cell growth and stimulation of these cells.TSH inhibits the IGFBP-3 secretion, whereas inhibitors ofthyroid gland functions generally increase its synthesis (5).

Some mechanisms suggest that thyroid hormones havea stimulator effect on circulating IGF-I by both in vivoand in vitro data. In adult hypothyroidism animal studies,it was shown that plasma IGF-I and IGFBP-3 are mainlysynthesized and secreted by the liver in response to stimu-lation by growth hormone (GH). Nevertheless, althoughthyroid hormone regulates GH gene expression, not allthe effects of thyroid hormone on the IGF-I is GH medi-ated. (11). Changes in thyroid status have a major effecton the GH/IGF axis. Thyroid hormones in turn modifythe IGF-I system in a variety of ways including a centraleffect on GH secretion (12). It has also been known thatthe effects of thyroid hormones on IGF-I synthesis andsecretion are mediated by insulin in neonatal hypothyroidrats, whereas GH mediates thyroid actions in adult rats (13).

Physiological roles of IGF-I (CA)19 and IGFBP-3e202 A/C gene polymorphisms have not yet been identified in variousdiseases. This is a preliminary study and it is apparent thatfurther studies are required for the elucidation of thissituation. Some studies that researched effects of this poly-morphism on different tissues and cells, especially cancercells, have been found and reported various effects. Studieshave been performed that indicated an increase or decreasein circulation concentration. For example, it has beenreported that the IGF system plays an important role in thegrowth of thyroid cancer cells, and IGF-I expression isincreased in thyroid tumors as reported in one study (14).

IGF-I and IGFBP-3 stimulate growth, and their actualphysiological roles in thyroid gland and thyroid hormoneshave not yet been explained. IGF-I and IGFBP-3 gene poly-morphism affect the functions of these factors. IGF-I(CA)19 and IGFBP-3e202 A/C gene polymorphisms havenot previously been studied in thyroid disease. In this study,we aimed to evaluate the relationship between thyroidhormone and genotype variations by investigating theeffects of IGF-I and IGFBP-3 gene polymorphism on hypo-and hyperthyroidism patients.

Materials and Methods

Thirty seven hyperthyroid and 76 hypothyroid patients di-agnosed at the Endocrinology Clinic of PamukkaleUniversity hospital were included in the study (15).Exclusion criteria for the control group included historyof thyroid disease, thyroid autoantibody positivity, and ab-normal thyroid hormone levels, being treated with thyroidhormone, antithyroid drugs or any drug that might affectevaluation of thyroid status. Written inform consent wasobtained and blood samples were collected voluntarily.Thyroid hormone levels during the diagnosis of hypo-and hyperthyroidisms were used. Two ml of peripheralblood samples were drawn in tubes with EDTA for DNAisolation. Isolation was performed with classic phenol-chloroform extraction method (16).

Analysis of IGF-I (CA)19 Polymorphic Area

PCR analysis was performed in the genomic DNAs isolatedby using proper primers for the IGF-I (CA)19 area (forwardprimer 50-GCTAGCCAGCTGGTGTTATT-30 and reverseprimer 50-ACCACTCTGGGAGAAGGGTA-30) (17). Theseprimers extend the repeated cytosine-adenine (CA)n poly-morphic area just above the 1 kb of human IGF-I gene.A 0.5 ng/mL of genomic DNA sample obtained from theperipheral leukocytes was added to the reaction mixture.The mixture also included 0.5 nmol/L forward primer, 0.5nmol/L reverse primer, 0.2 mmol/L dNTP, 1.5 mmol/LMgCl2, 10X PCR buffer, 0.025 U/mL Taq DNA polymerase.A total of 50 mL of PCR volume was used in the study. Theprocedure was as follows: denaturation at 95�C for 3 minand 94�C for 45 sec, annealing at 57�C for 45 sec, extensionat 72�C for 1 min for a total of 30 cycles and waiting at 72�Cfor 10 min in a stepwise manner. Samples were kept at 4�Cuntil analysis. Electrophoresis was then done by applyingthe samples on 3.5% agarose gel, and the resulting bandswere evaluated with UV gel documentation system.

Analysis of IGFBP-3 e202 A/C Polymorphism

Single nucleotide polymorphism in the promoter regionof IGFBP-3 genee202 A/C area was analyzed by themethod of Schildkraut et al. (17). The region obtained fromthe genomic DNAs was amplified with proper primers in

44 Kursunluoglu et al. / Archives of Medical Research 40 (2009) 42e47

PCR (method). PCR mixture included 30 ng genomic DNA,0.5 nmol/L forward primer (50-CCACGAGGTACACAC-GAATG-30), 0.5 nmol/L reverse primer (50-AGCCG-CAGTGCTCGCATCTGG-30), 0.2 mmol/L dNTP, 1.5mmol/L MgCl2, 10X PCR buffer, 0.025 U/mL Taq DNApolymerase; 50 mL of total PCR volume was studied. PCRconditions were hot start at 95�C for 10 min and 96�C for30 sec, 64�C for 30 sec, 72�C for 1 min; the procedure wasrepeated 35 times. Duration of waiting time was 5 min at72�C. The products obtained were visualized in 2% agarosegel and then the 459 bp of PCR products were digested withAlw21I restriction enzyme at 37�C during the night. The re-stricted products were electrophoresed in 3% of agarose gelcontaining ethidium bromide. Gels were visualized with theUV gel documentation system, bands were evaluated, andthe genotyping was done. Evaluation of allele naming was242-162 bp AA, 288-162 bp CC, 288-242-162 bp AC.

Biochemical Analysis

Serum samples were obtained from the 6 ml of blood takenfrom the hypo- and hyperthyroid patients, and serum freeT3 (fT3), free T4 (fT4), thyroid stimulating hormone(TSH), anti-thyroglobulin (anti-Tg) and anti-thyroid perox-idase (anti-TPO) levels were determined with the chemilu-minescence method in an immunanalyzer (Immulite 2000,Diagnostic Products, Los Angeles, CA).

Statistical Analysis

Statistical analysis was done with SPSS (Statistical Packagefor Social Sciences) v.10.0 pocket program. All results weregiven as mean� standard error. Evaluations related to geno-type distribution between groups were tested with c2 test.Comparisons among groups were done with Kruskal-Wallistest, and between groups with Mann-Whitney U test. Valuesof p !0.05 were accepted as statistically significant.

Table 2. Genotype distribution of IGF-I and IGFBP-3 gene

polymorphism in the control, hypo- and hyperthyroidism groups

Hyperthyroidism n (%) Hypothyroidism n (%) Control n (%)

Results

In this study, serum fT3, fT4, TSH, anti-Tg and anti-TPOlevels of hypo- and hyperthyroid patients were compared(Table 1). The range of normal values in controls for these pa-rameters is fT3, 2�4.4 pg/mL; fT4, 0.93�1.7 ng/dL; TSH,0.27�4.2 lU/mL; anti-Tg, 0�115 IU/mL; and anti-TPO,

Table 1. Hormone levels of hypo- and hyperthyroidism patients

Hyperthyroidism (n 5 37) Hypothyroidism (n 5 76) p

fT3 6.79 � 5.09 2.53 � 0.73 0.001

fT4 2.69 � 1.45 0.97 � 0.33 0.001

TSH 0.01 � 0.02 17.95 � 36.48 0.04

Anti-Tg 266.10 � 324.54 351.93 � 506.28 0.349

Anti-TPO 188.93 � 160.23 318.88 � 319.45 0.22

TSH, thyroid-stimulating hormone; Anti-Tg, anti-thyroglobulin; Anti-TPO,

anti-thyroid peroxidase.

0�34 IU/mL. According to our results, serum fT3, fT4 andTSH levels were significantly different ( p !0.05) betweenthe two patient groups, whereas no significant difference inanti-Tg and anti-TPO levels was found between groups.

In our study, the difference among genotype distribution(192�194 bp, !192 bp, O194 bp) identifying IGF-I(CA)19 region of hypothyroidism patients, hyperthyroidismpatients and controls was found to be statistically signifi-cant (Table 2). With these results, O194 bp genotypefrequencies of hypothyroidism, hyperthyroidism andcontrol groups were observed as 81.6, 51.4 and 72%,respectively. The 192�194 bp genotype frequencies were3.9, 13.5 and 6%, respectively. In addition, they were14.5, 35.1 and 22% for the !192 bp genotype distribution.When we compared the genotype distribution betweengroups, the difference in genotype distribution for IGF-I(CA)19 gene polymorphism between hypo- and hyperthy-roidism patients was statistically significant (c2 5 11.39,df 5 2, p 5 0.003), wheras there was no difference inthe genotype distribution of controls and patient groups.

In hyperthyroidism groups, fT3, fT4, TSH, anti-Tg andanti-TPO levels among the three IGF-I genotypes(192�194, !192 and O194) did not demonstrate any signif-icant difference according to Kruskal-Wallis test. But a sig-nificant difference in serum fT4 levels between twogenotypes (192�194 and !192) was demonstrated (Mann-Whitney U test) (Table 3). In the hypothyroidism group, nosignificant difference was observed in the levels of the mea-sured hormones between and among groups (Table 4). Thedifference in the genotype distribution (AA, AC, and CC)identifying IGFBP-3e202 A/C region of hypothyroidism,hyperthyroidism and control groups was studied (Table 2).According to these results, AA genotype frequencies of hy-pothyroidism, hyperthyroidism and control groups were10.6, 17.2 and 9.1%, respectively. AC genotype frequenciesof the groups were 63.8, 34.5 and 47.7%, respectively,whereas they were 25.5, 48.3 and 43.2%, respectively, forthe CC genotype frequency. The observed and expectedfrequencies of IGFBP-3 genotypes conformed to the

IGF-I

192�194 5 (13.5) 3 (3.9) 3 (6.0)

!192 13 (35.1) 11 (14.5) 11 (22)

O194 19 (51.4) 62 (81.6) 36 (72)

c2 5 11.55, df 5 4, p 5 0.021

IGFBP-3

AA 5 (17.2) 5 (10.6) 4 (9.1)

AC 10 (34.5) 30 (63.8) 21 (47.7)

CC 14 (48.3) 12 (25.5) 19 (43.2)

c2 5 7.30, df 5 4, p 5 0.120

IGF, insulin-like growth factors; IGFBP, insulin-like growth factor binding

proteins.

Table 3. Hormone levels among the IGF-I genotype in

hyperthyroidism group

Hyperthyroidism IGF-I (CA)19 genotype

192e194 !192 O194

fT3 4.11 � 1.67 7.87 � 6.33 6.76 � 4.66

fT4 1.92 � 0.80a 2.88 � 1.57a 2.76 � 1.53

TSH 0.02 � 0.02 0.01 � 0.01 0.01 � 0.02

Anti-Tg 132.55 � 75 340.30 � 362.43 250.48 � 335.62

Anti-TPO 218.68 � 201.87 204.16 � 158.61 170.68 � 157.35

Age (years) 48.00 � 0.03 37.00 � 12.12 51.33 � 12.20

Male 2 1 9

Female 3 12 10

aIn each line the difference between the means with same letters are sig-

nificant, p !0.05 (Mann-Whitney U test).

Table 5. Hormone levels among the IGFBP-3 genotype in

hyperthyroidism group

Hyperthyroidism IGFBP-3e202 A/C genotype

AA AC CC

fT3 4.95 � 1.51 5.12 � 1.97 6.86 � 4.66

fT4 2.19 � 0.30 2.20 � 0.88 2.73 � 1.32

TSH 0.01 � 0.006 0.01 � 0.005 0.01 � 0.02

Anti-Tg 206.00 � 123.96 325.00 � 433.06 158.19 � 151.49

Anti-TPO 201.60 � 214.98 188.93 � 171.63 189 .56 � 163.35

Age (years) 48.00 � 0.10 56.00 � 0.20 48.33 � 15.27

Male 1 4 3

Female 4 6 11

45Associations with Hyper- and Hypothyroidism of IGF-I and IGFBP-3

Hardy-Weinberg equilibrium in our study groups. With thecomparison of genotype distributions between groups, thedifference was statistically significant for IGFBP-3 e202gene polymorphism between hypothyroidism and hyperthy-roidism groups (c2 5 6.24, df 5 2, p 5 0.044), whereas it wasnot significant between the controls and the patient groups.

The fT3, fT4, TSH, anti-Tg and anti-TPO levels of hy-perthyroidism patients showed no significant differenceamong the three IGFBP-3 genotypes: AA, AC, and CC.There was also no difference between groups in terms ofhormone levels (Table 5).

Hormone levels (fT3, fT4, TSH, anti-Tg, anti-TPO) ofhypothyroid patients did not display important differencesamong the AA, AC and CC genotypes of IGFBP-3. SerumTSH levels between AA and AC genotypes differed signif-icantly ( p 5 0.019) (Table 6).

Table 6. Hormone levels among the IGFBP-3 genotype in

hypothyroidism group

Discussion

Endocrine, paracrine, and autocrine characteristics of IGF-Iare possible within the thyroid. IGF-I and thyroid hormonesare molecules that promote growth, development and me-tabolism (4). It is known that thyroid hormones play impor-tant roles in the regulation of IGF-I and IGFBP-3. Thyroidcells have IGF-I receptors and synthesize and secrete bothIGF-I and IGFBP-3. IGF-I and IGFBP-3 are also importantfor the normal thyroid follicular cell development and func-

Table 4. Hormone levels among the IGF-I genotype in hypothyroidism

group

Hypothyroidism IGF-I (CA)19 genotype

192�194 !192 O194

fT3 2.34 � 0.99 2.42 � 0.62 2.56 � 0.74

fT4 0.80 � 0.57 0.93 � 0.32 0.99 � 0.32

TSH 24.93 � 18.35 24.09 � 26.67 17.95 � 38.80

Anti-Tg 523.66 � 361.89 362.24 � 386.54 341.79 � 533.65

Anti-TPO 507.26 � 531.83 187.80 � 216.25 333.02 � 321.69

Age (years) 49.00 � 0.30 43.00 � 8.45 47.82 � 10.50

Male 1 1 10

Female 2 11 52

tion in vitro. IGF-I participates in the regulation of thyroidgrowth and function (4).

IGF-I and IGFBP-3 stimulate the growth and precisephysiological roles of these factors on the thyroid glandand its hormones are not yet understood. Gene polymor-phisms related to IGF-I and IGFBP-3 affect their functions.

In the study by Bleumink et al. (18), it was shown that to-tal IGF-I levels in circulation decreased in polymorphic sub-jects who did not have the IGF-I gene allele. At the sametime, serum IGF-I levels of subjects having 192�194 bp al-leles increased, whereas IGF-I levels decreased in subjectswith !192 bp and O194 bp alleles (18). In addition, ina study performed on hypothyroid patients, it has been re-ported that serum IGF-I levels were low, IGF-I activity de-creased, and the endocrine and paracrine effects of IGF-Iwere distributed. Children with hypothyroidism displayedretarded growth and development attributed to the decreasein the activity of GH/IGF-I axes (19).

In a study performed on middle-aged males with osteopo-rosis (20), the authors found that serum IGF-I concentrationsof subjects with 192�194 genotypes were 20% lower thanthose with other genotypes. In addition, they showed that se-rum IGF-I levels decreased in healthy men and women with192�194 genotypes (20). In another study on healthy adultmales, Allen et al. (21) observed that IGF-I (CA)19 gene poly-morphism was not related to IGF-I concentrations (21). The

Hypothyroidism IGFBP-3e202 A/C genotype

AA AC CC

fT3 2.67 � 0.53 2.52 � 0.57 2.76 � 0.37

fT4 0.86 � 0.17 1.00 � 0.24 1.02 � 0.31

TSH 14.50 � 7.03a 11.48 � 16.36a 13.88 � 14.72

Anti-Tg 333.20 � 160.84 426.40 � 740.38 373.10 � 292.03

Anti-TPO 293.76 � 119.89 263.23 � 243.97 269.18 � 265.18

Age (years) 50.00 � 2.82 48.00 � 5.63 45.83 � 9.70

Male 1 4 2

Female 4 26 10

aIn each line the difference between the means with same letters are sig-

nificant, p !0.05 (Mann-Whitney U test).

46 Kursunluoglu et al. / Archives of Medical Research 40 (2009) 42e47

high value of O194 genotype frequency found in our studysuggested that IGF-I levels may be low in these patients. Thy-roid hormone levels may be decreased and play roles in hy-pothyroidism, depending on the low levels of IGF-I. Thereare IGF-I binding sites on thyroid cells and thyroid cells ex-press both IGF-I and IGF-I receptor proteins (22). With thebinding of IGF-I to its receptors on thyroid cells, develop-ment and functions of thyroid cells are affected (22). Thyroidhormones may play an independent role in the regulation ofIGF-IR expression or signals. IGF-I affects its target tissuesby binding to its receptors. Thyroid hormones increase theregulation of IGF-IR and IGFBP-3 cultured from thehypophysis, and the increase in the levels of thyroid hor-mones increases the binding of IGF-I to the erythrocyte mem-brane. It has been known that hypothyroidism causes thedistributed expression of IGF-IR in target tissues. Addition-ally, it has been thought that the disruption of IGF-IR synthe-sis or signals in hypothyroidism may be due to the disruptionof recombinant IGF-I/IGFBP-3 complex (11). It has beenfound that serum levels of IGF-I and IGFBP-3 in hypothy-roidism decreased and recovered with the use of GH andthyroid hormones, returning to normal basal values (11).

It has been reported that serum IGF-I levels of hyperthy-roidism patients were high (19), and direct effects ofthyroid hormones on IGF-I production have been shown inexperimental studies in vitro (23). It has been reported in an-other study that increases in IGF-I in circulation led to the for-mation of goiter (24). In this study, it was shown that goiterformation occurred in transgenic rats expressing IGF-I andIGF-IR in thyroid gland. Thyroid hormone levels increasedin circulation, whereas TSH concentration decreased (24).In one study it has been shown that IGF-I levels of subjectswith !192 genotype were found to be low (25). Also, in an-other study it has been stated that minor physiologicalchanges in serum T4 levels may be positively correlated withserum IGF-I levels (4). In a study by Klinger et al. (26) per-formed with healthy subjects, they observed that somato-statin release increased, and serum TSH levels decreasedwith the use of IGF-I. In addition, it has been known thatIGF-I stimulates the peripheral conversion of T4eT3 (26).Seck et al. (27) reported that serum fT4 concentrations of50 healthy males and 80 healthy females were positively re-lated to the IGF-I levels in the circulation. They also observedthat IGF-I levels of females in their study were negativelycorrelated with fT3/fT4 ratio. The reason for this situationhas been attributed to the fact that serum IGF-I is related onlyto fT4 levels (27). In a study performed on rats subjected tothyroidectomy and treated with T4, it was shown that therewas good correlation between thyroid hormones and IGF-IIduring the neonatal period and between thyroid hormonesand IGF-I in adult rats (19). Use of T4 to hypophysectomizedand thyroidectomized rats stimulates IGF activities in the ab-sence of GH. In such a study, growth disorders have been ob-served in humans and animals with the use of GH in theabsence of T4 (19).

T3, one of the thyroid hormones, stimulates IGF-Iproduction in various tissues and organs (28). It causesIGF-I mRNA levels to increase in osteoblastic cells andstimulates IGF-I release from bone tissue. In addition,IGF-I increases the protein levels in bone tissue. In thethyroid gland, IGF-I stimulates fibroblasts, follicular cellsand endothelial cells. The interaction between IGF-I andTSH is required for the stimulation of follicular cell growthand functions. TSH inhibits IGFBP-3 secretion. IGF-I stim-ulates reproduction, whereas T3 diminishes hypertrophicdifferentiation (28).

It has been stated in another study that IGFBP-3 e202 A/Cpolymorphism may affect the levels of IGFBP-3 in circula-tion, especially serum IGFBP-3 levels of patients with AAgenotype that were high, whereas those with CC genotypedecreased (21). In another study, various disease groups, al-though no significant correlation was found in the A/C poly-morphism of IGFBP-3 e202 promoter area between patientgroups and controls, serum IGFBP-3 levels of patients withCC genotype were low. This situation was important for thedevelopment and progression of various diseases (29). Addi-tionally IGFBP-3 (C e202A) polymorphism is related to theserum IGFBP-3 in circulation. In a study by Al-Zahrani et al.(30) on breast cancer, it was found that the disease risk forsubjects with AA genotype decreased, and the increase inthe IGFBP-3 levels protected the body from various diseases.In addition, it was seen that the disease risk increased inpatients with AC or CC genotypes (30). The high value ofAC genotype frequency found in our study suggested thatthe IGFBP-3 levels may be low in hypothyroid patients.Thyroid hormone levels may be decreased and play roles inthe occurrence of hypothyroidism, depending on the lowlevels of IGFBP-3. It has been observed that the decreasein plasma IGFBP-3 concentrations of hypothyroid rats isrelated to the decrease in liver IGFBP-3 mRNA levels (28).Most of the IGF-I binds to IGFBP-3 in circulation. Decreasein serum IGFBP-3 causes rapid clearance of IGF-I fromcirculation. Stimulatory effects of surplus IGF-I may beintermediary in thyroid functions in bone and muscle tissues(31). In the same way, serum IGFBP-3 levels were low incongenital hypothyroidism, and the values increased afterthyroid hormone administration (28).

In a study by Belsing et al. (32), a negative correlation wasfound between total T4 and IGFBP-3. It has been shown thatTSH receptor antibodies were not related to IGFBP-3,whereas there was a positive relationship between IGF-I re-leasing peptides and thyroid antibodies as well as anti-TPO(32). The reason for these differences is not known. However,it has been thought that this may be due to factors such as dif-ferent use of total or free thyroid hormones, changes in thenumber of IGF-R, interaction among anabolic effects ofIGF-releasing peptides, thyrotoxic conditions, feeding re-gime and energy intake. Thus, the metabolic process in thesepatients may be affected by IGF-I and IGFBP-3 levels in cir-culation (32). There were no significant changes in anti-Tg

47Associations with Hyper- and Hypothyroidism of IGF-I and IGFBP-3

and anti-TPO levels of these groups in terms of genotype dis-tributions identifying both IGF-I (CA)19 and IGFBP-3 -202A/C regions in our study.

Although there have been many studies reported in theliterature related to the relationship between IGF-I andIGFBP-3, this is the first study on IGF-I (CA)19 andIGFBP-3 A/C gene polymorphism in hypo- and hyperthy-roidism. Based on these preliminary results, we can say thatIGF-I (CA)19 and IGFBP-3 A/C gene polymorphism maybe risk factors for thyroid disorders. Further comprehensivestudies are required in order to clarify this situation in thy-roid diseases.

AcknowledgmentsThis study was supported by Pamukkale University Research Fund(Project no: 2007 SBE003).

References1. Maran RR. Thyroid hormones: their role in testicular steroidogenesis.

Arch Androl 2003;49:375e388.

2. Decuypere E, Van Asa P, Van der Geyten S, Darras VM. Thyroid hor-

mone availability and activity in avian species. Domestic Anim Endo-

crinol 2005;29:63e77.

3. Calvo R, Obregon MJ, Ruiz de Ona C, Escobar del Rey F, Morreale de

Escobar G. Congenital hypothyroidism, as studied in rats. Crucial role

of maternal thyroxine but not 3,5,30-triiodothyronine in the protection

of the fetal brain. J Clin Invest 1990;86:889e899.

4. Wang JF. The interaction of thyroid stimulating hormone (TSH), insu-lin-like growth factors (IGFs), and insulin-like growth factor binding

proteins (IGFBPs) in the regulation of the synthesis and secretion of

thyroid hormones by cultured sheep thyroid cells. [doctoral thesis].

London, Ontario, Canada: University of Western Ontario; 1995.

5. Vesely D, Astl J, Latuvka P, Matucha P, Betka J. Serum levels of IGF-

I, HGF, TGFb1, bFGF and VEGF in thyroid gland tumors. Physiol Res

2004;53:83e89.

6. Baker J, Liu JP, Robertson EJ, Efstratiadis A. Role of insulin-like growth

factors in embryonic and postnatal growth. Cell 1993;75:73e82.

7. Turgut S, Kaptanoglu B, Emmungil G, Turgut G. Increased plasma

levels of growth hormone, insulin-like growth factor (IGF)-I and

IGF-binding protein 3 in pregnant rats with exercise. Tohoku J Exp

Med 2006;208:75e81.

8. Turgut G, Kaptanoglu B, Turgut S, Genc O, Tekinturk S. Influence of

acute exercise on urinary protein, creatinine, insulin-like growth fac-

tor-I (IGF-I) and IGF binding protein-3 concentration in children.

Tohoku J Exp Med 2003;201:165e170.

9. Torres-Aleman I. Insulin-like growth factors as mediators of functional

plasticity in the adult brain. Horm Metab Res 1999;31:114e119.

10. Iglesias P, Bayon C, Mendez J, Gancedo PG, Grande C, Diez JJ.

Serum insulin-like growth factor type 1, insulin-like growth factor-

binding protein-1, and insulin-like growth factor-binding protein-3

concentrations in patients with thyroid dysfunction. Thyroid 2001;

11:1043e1048.

11. Nanato-Salonen K, Muller HL, Hoffmann AR, Vu TH, Rosenfeld RG.

Mechanisms of thyroid hormone action on the insulin-like growth fac-

tor system: all thyroid hormone effects are not growth mediated.

Endocrinology 1993;132:781e788.

12. Rodriguez-Arnao J, Miell JP, Ross RJM. Influence of thyroid hormones

on the GH-IGF-I axis. Trends Endocrinol Metab 1993;4:169e173.

13. Ramos S, Goya L, Martin MA, Escriva F, Pascual-Leone AM.

Influence of hypothyroidism on circulating concentrations and liver

expression of IGF-binding proteins mRNA from neonatal and adult

rats. J Endocrinol 2002;172:363e373.

14. Maiorano E, Ciampolillo A, Viale G, Maisonneuve P, Ambrosi A,

Triggiani V, et al. Insulin-like growth factor 1 expression in thyroid

tumors. Appl Immunohistochem Mol Morphol 2000;8:110e119.

15. Simmonds MJ, Heward JM, Carr-Smith J. Contribution of single nucle-

otide polymorphisms within FCRL3 and MAP3K7IP2 to the pathogen-

esis of Graves’ disease. J Clin Endocrinol Metab 2006;91:1056e1061.

16. Ponez M, Solowiejczyk D, Harpel B, Mory Y, Schwartz E, Surrey S.

Construction of human gene libraries from small amounts of periph-

eral blood. Hemoglobin 1982;6:27e36.

17. Schildkraut JM, Wahnefried WD, Wenham RM, Grubber J, Jeffreys AS,

Grambow SC, et al. IGF1 (CA)19 repeat and IGFBP3 -202 A/C geno-

types and the risk of prostate cancer in black and white men. Cancer Epi-

demiol Biomarkers Prev 2005;14:403e408.

18. Bleumink GS, Rietveld I, Janssen JA, van Rossum EF, Deckers JW,

Hoffman A, et al. Insulin-like growth factor-I gene polymorphism

and risk of heart failure. Am J Cardiol 2004;94:384e386.

19. Ramos S, Goya L, Alvarez C, Martın MA, Pascual-Leone AM. Effect of

thyroxine administration on the IGF/IGF binding protein system in neo-

natal and adult thyroidectomized rats. J Endocrinol 2001;169:111e122.

20. Rosen CJ, Kurland ES, Vereault D. Association between serum insulin

growth factor-I (IGF-I) and a simple sequence repeat in IGF-I gene:

implications for genetic studies of bone mineral density. J Clin Endo-

crinol Metab 1998;83:2286e2290.

21. Allen NE, Davey GK, Key TJ, Zhang S, Narod SA. Serum insulin like

growth factor I (IGF-I) concentration in men is not associated with the

cytosine-adenosine repeat polymorphism of the IGF-I gene. Cancer

Epidemiol Biomarkers Prev 2002;11:319e320.

22. Dumont JE, Maenhaut C, Pirson I, Baptist M, Roger PP. Growth fac-

tors controlling the thyroid gland. Bailliere’s Clin Endocrinol Metabol

1991;5:727e755.

23. Amit T, Hertz P, Ish Shalom S. Effects of hypo- and hyperthyroidism

on growth hormone binding protein. Clin Endocrinol 1991;35:

159e162.

24. Jing W, Grunler J, Lewitt MS. Gender-specific pattern of insulin-like

growth factor-binding protein-3 protease activity in mouse thyroid.

Endocrinology 2004;145:1137e1143.

25. Kato I, Eastham J, Li B, Smith M, Yu H. Genotypeephenotype anal-

ysis for the polymorphic CA repeat in the insulin-like growth factor-I

(IGF-I) gene. Eur J Epidemiol 2003;18:203e209.

26. Klinger B, Ionesco A, Anin S, Laron Z. Effect of insulin-like growth

factor I on the thyroid axis in patients with Laron-type dwarfism and

healthy subjects. Acta Endocrinol 1992;127:515e519.

27. Seck T, Nave C, Ziegler R, Pfeilschifter J. Positive association between

circulating free thyroxine and insulin-like growth factor I concentrations

in euthyroid elderly individuals. Clin Endocrinol 1998;48:361e366.

28. Robson H, Siebler T, Shalet SM, Williams GR. Interactions between

GH, IGF-I, glucocorticoids, and thyroid hormones during skeletal

growth. Pediatr Res 2002;52:137e147.

29. Wang L, Habuchi T, Tsuchiya N, Mitsumori K, Ohyama C, Sato K,

et al. Insulin-like growth factor-binding protein-3 gene -202 A/C poly-

morphism is correlated with advanced disease status in prostate can-

cer. Cancer Res 2003;63:4407e4411.

30. Al-Zahrani A, Sandhu MS, Luben R, Thompson D, Baynes C,

Pooley K, et al. IGF1 and IGFBP3 tagging polymorphisms are associ-

ated with circulating levels of IGF1, IGFBP3 and risk of breast cancer.

Hum Mol Gen 2006;15:1e10.

31. Svanberg E, Healey J, Mascarenhas D. Anabolic effects of rhIGF-

I/IGFBP-3 in vivo are influenced by thyroid status. Eur J Clin _Invest

2001;31:329e336.

32. Zimmermann-Belsing T, Juul A. Juul Holst J, Feldt-Rasmussen U.The

insulin-like growth axis in patients with autoimmune thyrotoxicosis:

effect of antithyroid drug treatment. Growth Horm-IGF Res 2004;

14:235e244.