Thyroid hormone modulates insulin-like growth factor-I(IGF-I) and IGF-binding protein-3, without mediation by growth hormone, in patients with autoimmune thyroid diseases

The causal relationship between autoimmune thyroid disorders and telomere length: A Mendelian randomization and colocalization study

This study aimed to evaluate whether there is a causal relationship between autoimmune thyroid disorders (AITDs) and telomere length (TL) in the European population and whether there is reverse causality. In this study, Mendelian randomization (MR) and colocalization analysis were conducted to assess the potential causal relationship between AITDs and TL using summary statistics from large-scale genome-wide association studies, followed by analysis of the relationship between TL and thyroid stimulating hormone and free thyroxine (FT4) to help interpret the findings. The inverse variance weighted (IVW) method was used to estimate the causal estimates. The weighted median, MR-Egger and leave-one-out methods were used as sensitivity analyses. The IVW method results showed a significant causal relationship between autoimmune hyperthyroidism and TL (β = -1.93 × 10-2 ; p = 4.54 × 10-5 ). There was no causal relationship between autoimmune hypothyroidism and TL (β = -3.99 × 10-3 ; p = 0.324). The results of the reverse MR analysis showed that genetically TL had a significant causal relationship on autoimmune hyperthyroidism (IVW: odds ratio (OR) = 0.49; p = 2.83 × 10-4 ) and autoimmune hypothyroidism (IVW: OR = 0.86; p = 7.46 × 10-3 ). Both horizontal pleiotropy and heterogeneity tests indicated the validity of our bidirectional MR study. Finally, colocalization analysis suggested that there were shared causal variants between autoimmune hyperthyroidism and TL, further highlighting the robustness of the results. In conclusion, autoimmune hyperthyroidism may accelerate telomere attrition, and telomere attrition is a causal factor for AITDs.

Synergistic effects of hormones on structural and functional maturation of cardiomyocytes and implications for heart regeneration

The limited endogenous regenerative capacity of the human heart renders cardiovascular diseases a major health threat, thus motivating intense research on in vitro heart cell generation and cell replacement therapies. However, so far, in vitro-generated cardiomyocytes share a rather fetal phenotype, limiting their utility for drug testing and cell-based heart repair. Various strategies to foster cellular maturation provide some success, but fully matured cardiomyocytes are still to be achieved. Today, several hormones are recognized for their effects on cardiomyocyte proliferation, differentiation, and function. Here, we will discuss how the endocrine system impacts cardiomyocyte maturation. After detailing which features characterize a mature phenotype, we will contemplate hormones most promising to induce such a phenotype, the routes of their action, and experimental evidence for their significance in this process. Due to their pleiotropic effects, hormones might be not only valuable to improve in vitro heart cell generation but also beneficial for in vivo heart regeneration. Accordingly, we will also contemplate how the presented hormones might be exploited for hormone-based regenerative therapies.

The Prospective Association Between Plasma Concentrations of Cellular Growth Factors and Risk of Heart Failure Mortality in Japanese Population

Background

Limited evidence is available on the association of insulin-like growth factors (IGFs) and risk of heart failure in population-based samples. We investigated whether serum IGFs concentrations can predict mortality from heart failure.

Methods

We conducted a nested case-control study of 39,242 subjects aged 40–79 years who participated in the JACC study, a large Japanese prospective cohort study; participants provided serum samples and were followed up for 9 years. In heart failure cases and age-, sex-, community-, and year of blood withdrawal-matched controls, we measured serum concentrations of IGF-I, IGF-II, and IGF binding protein 3 (IGFBP3) and transforming growth factor (TGF-β1).

Results

During the follow-up, there were 88 heart failure deaths (44 men and 44 women). Each increment of 1 standard deviation [SD] of IGF-II (120.0 ng/mL in women and 143.7 ng/mL in men) was associated with a 47% reduced risk of mortality from heart failure; multivariable odds ratio was 0.53 (95% confidence interval [CI], 0.30–0.94, P-trend = 0.03). The multivariable odds ratio in the highest quartile of IGFBP3 serum concentrations (≥3.29 µg/mL in women and ≥3.31 µg/mL in men) compared with the lowest (<2.11 µg/mL in women and <2.56 µg/mL in men) was 0.24 (95% CI, 0.05–1.11; P-trend = 0.12). No association was found between serum concentrations of IGF-I or TGF-β1 and risk of heart failure.

Conclusions

Higher serum concentrations of IGF-II were associated with lower mortality from heart failure, which might suggest a possible role of IGF-II in the occurrence or prognosis of heart failure.

Serum levels of insulin-like growth factor 1 are negatively associated with log transformation of thyroid-stimulating hormone in Graves' disease patients with hyperthyroidism or subjects with euthyroidism: A prospective observational study

Insulin-like growth factor 1 (IGF-1) has a molecular structure similar to that of insulin. As an essential mediator of growth hormone, IGF-1 plays a vital role in growth of children and anabolic effects of adults. We evaluated the serum levels of IGF-1 in patients with hyperthyroidism or euthyroidism.In this study, 30 patients each of Graves' disease with hyperthyroidism (HY group) and euthyroid individuals (EU group) were recruited. The HY patients were treated with antithyroid regimens as clinically indicated. No medications were given to EU patients. The demographic characteristics and anthropometric and laboratory data of both groups at baseline and 6 months were compared. Associations between levels of IGF-1 and free thyroxine (fT4), thyroid-stimulating hormone (TSH), or log transformation of TSH (logTSH) were analyzed.At baseline, the HY patients had significantly higher serum IGF-1 levels than EU patients (median [Q1, Q3]: 305.4 [257.4, 368.1] vs. 236.7 [184.6, 318.8] ng/mL, P = .007). At 6 months, the HY patients still had higher serum levels of IGF-1 than EU patients (299.5 [249.9, 397.9] vs 222.1 [190.2, 305.4] ng/mL, P = .003). At baseline, the serum levels of IGF-1 in the HY and EU patients were positively associated with fT4 (β = 29.02, P = .002) and negatively associated with TSH (β = -31.46, P = .042) and logTSH (β = -29.04, P = .007). The associations between serum levels of IGF-1 with fT4 or TSH became insignificant at 6 months. However, the serum IGF-1 levels had persistent negative associations with logTSH at 6 months (β = -26.65, P = .021). The negative associations between IGF-1 and logTSH at baseline and 6 months remained significant even after adjustment with sex and age (β = -20.22, P = .023 and β = -20.51, P = .024, respectively).The HY patients had higher serum IGF-1 levels than EU patients. The serum IGF-1 concentrations were negatively associated with logTSH in patients with hyperthyroidism or euthyroidism.

Thyroid function in children with growth hormone deficiency during long-term growth hormone replacement therapy

AIM OF THE STUDY

The aim of this study was to investigate the effects of growth hormone (GH) therapy on thyroid function in a group of euthyroid children with isolated idiopathic growth hormone deficiency (GHD).

MATERIAL AND METHODS

The study was retrospective and included 117 children treated with GH for 1-4 years. Anthropometric measurements and serum concentrations of insulin-like growth factor-1 (IGF-1), thyroid-stimulating hormone (TSH), and free thyroxine (fT4) were analysed at baseline and during GH therapy.

RESULTS

TSH levels did not change significantly after the initiation of GH treatment, while fT4 levels decreased after the second year of GH treatment (p < 0.01) and remained lower than baseline until the end of observation (p < 0.01, after both the third and fourth year of therapy) in the whole group. Analysis according to baseline pubertal status revealed significant changes in TSH and fT4 levels during GH treatment, but only in the prepubertal children. Multiple regression analysis confirmed that mean GH doses administered in the first two years of GH therapy were independently (R = 0.218, p < 0.05) associated with changes in fT4 levels in this period (∆fT42 years - baseline), even when taking into account changes in height SDS and bone age.

CONCLUSIONS

FT4 levels decreased during GH replacement therapy, while TSH levels appeared to be unaffected by GH therapy. Prepubertal children seem to be more predisposed to thyroid function alterations during such therapy in comparison to pubertal children. Changes in fT4 levels during GH replacement therapy are related to GH doses.

A genome-wide DNA methylation analysis in peripheral blood from patients identifies risk loci associated with Graves' orbitopathy

OBJECTIVE

Graves' orbitopathy (GO) is an inflammatory orbital disease of autoimmune origin with the potential to cause severe functional and psychosocial effects. The pathogenesis has not been fully elucidated. We investigated whether DNA methylation was associated with GO incidence in Chinese patients.

MATERIALS AND METHODS

Six GO patients and six age-matched controls were recruited, and genome-wide DNA methylation patterns were analyzed in their peripheral blood. t tests were performed to determine differential methylated sites in genomic regions and the univariable logistic regression analyses was performed to evaluate their risk with GO incidence. Cluster analysis and principal component analysis (PCA) were performed to determine the effects of the extracted differentially methylated sites.

RESULTS

One hundred and forty-eight differentially methylated sites were identified, including CD14 (fold change = 4.31, p = 0.005), IL17RE (fold change = 2.128, p = 0.005), and DRD4 (fold change = 0.25, p = 0.004), and were supported by cluster and PCA analyses. Univariable logistic regression analyses showed that the methylation patterns at 12 loci were associated with GO incidence. The relative risk per 1% decrease in methylation at ZCCHC6 and GLI3 was 0.15 (95% CI 0.03-0.91; p = 0.039) and 0.65 (95% CI 0.42-0.98; p = 0.042), respectively. Pearson correlation analyses demonstrated that methylation levels at IL17RE were positively associated with Clinical Activity Score (CAS) (r = 0.967, p < 0.05).

CONCLUSIONS

Our results demonstrate that differential methylation levels at analyzed sites (genes) may be risk markers of GO. DNA methylation analysis could provide new insights into understanding the disease and provide new treatment strategies for GO in Chinese patients.

Content of selected amino acids in the gastrocnemius muscle during experimental hypothyroidism in rats

Introduction: Thyroid hormones affect protein turnover, and in the case of hypothyroidism a decrease in protein synthesis and reduced release of certain amino acids from skeletal muscles are observed. Changes in the amino acid system of skeletal muscles may be responsible for the occurrence of muscle disorders. Material and Methods: The study measured the content of selected amino acids in the gastrocnemius muscle of Wistar rats during experimental hypothyroidism induced by oral administration of methimazole at a concentration of 0.05% in drinking water for 90 d. The rats were divided into four groups: E1 (n = 6) - experimental males, E2 (n = 6) - experimental females, C1 (n = 6) - control males, and C2 (n = 6) control females. Results: A statistically significant reduction occurred in leucine, isoleucine, and 1-methylhistidine levels in males, and 1-methylhistidine in females, in comparison to the control groups. Conclusion: The hypothyroidism-induced changes in amino acid content may be responsible for the occurrence of skeletal muscle function disorders.

Serum insulin-like growth factor type 1 concentrations in healthy dogs and dogs with spontaneous primary hypothyroidism

Circulating insulin-like growth factor type 1 (IGF-1) concentrations in dogs have been correlated with standard breed bodyweight (SBBW or breed size). Thyroid and somatotropic functions, which have common effects and regulatory mechanisms, were investigated in hypothyroid dogs. IGF-1 was measured in 495 adult healthy dogs (N) and in 220 primary hypothyroid dogs (HOT) with clinical and biological signs of primary hypothyroidism. IGF-1 was determined as a function of SBBW (kg): ≤15 (group A); 15<SBBW≤25 (group B); 25<SBBW≤40 (group C); and >40 (group D). In HOT dogs, median fT4 and c-TSH values were 9pmol/L and 1.5ng/mL, respectively. A significant correlation between bodyweight (BW) and IGF-1 was observed in both HOT and N dogs. The median IGF-1 value (ng/mL) was significantly higher (P<0.01) in HOT dogs compared to N in groups B, C and D (230 vs. 182; 316 vs. 230; 606 vs. 306 respectively). In conclusion, IGF-1 concentration should be interpreted in the context of SBBW in dogs and increases in spontaneous primary hypothyroidism. However, it remains unclear if this association is directly due to hypothyroidism or is the result of the weight gain accompanying hypothyroidism.

Serum IGF-1 and IGFBP-3 levels in subclinical hypothyroid women

Thyroid status is known to influence growth in mammals. The aim of this study is to investigate the possible relationship between autoimmune subclinical hypothyroidism and growth hormone (GH), insulin-like growth factor-1(IGF-1) and insulin-like growth factor binding protein-3(IGFBP-3) levels. Thirty-five women with autoimmune subclinical hypothyroidism, 33 years of age, were used as controls and enrolled in the study. Free triiodothyronin (FT3), free thyroxin(FT4), thyrotropin(TSH), anti-thyroid peroxidase(Anti-TPO), anti-thyroglobuline(Anti-Tg), GH, IGF-1 and IGFBP-3 levels were measured in blood samples and correlations among these parameters were evaluated. We found no significant differences in GH, IGF-1 or IGFBP-3 between patients and controls. In patients and controls, there were no correlations among thyroid hormones and IGF-1 or IGFBP-3 levels, but GH levels were correlated with FT3, FT4 and TSH only in patients’ group. In controls, only IGF-1 and IGFBP-3 levels were correlated. The present study suggests that subclinical hypothyroidism with high TSH and antibody status does not affect IGF-1 and IGFBP-3 levels in adult women. To our knowledge, this is the first study concerning the relationship between autoimmune subclinical hypothyroidism and IGF-1 and IGFBP-3 levels.

Do IGF-I concentrations better reflect growth hormone (GH) action in children with short stature than the results of GH stimulating tests? Evidence from the simultaneous assessment of thyroid function

Background

The diagnosis of growth hormone (GH) deficiency (GHD) in short children seems unquestionable when both GH peak in stimulating tests (GHST) and IGF-I concentration are decreased. However, the discrepancies between the results of GHST and IGF-I secretion are observed. It seems purposeful to determine the significance of GHST and IGF-I assessment in diagnosing GHD. The relationship between GH secretion and thyroid function, as well as GH influence on the peripheral thyroxine (T₄) to triiodothyronine (T₃) deiodination, mediated by IGF-I, were identified. Thus, clear differences in thyroid function between GH-deficient and non-GH-deficient subjects should exist.

Methods

Analysis comprised 800 children (541 boys), age 11.6 ± 3.1 years (mean ± SD), with short stature, in whom two (2) standard GHST (with clonidine and with glucagon) were performed and IGF-I, free T₄ (FT₄), free T₃ (FT₃) and TSH serum concentrations were assessed. The patients were qualified to the following groups: GHD - decreased GH peak in GHST and IGF-I SDS (n = 81), ISS - normal GH peak and IGF-I SDS (n = 347), low GH - normal IGF-I SDS, and decreased GH peak (n = 212), low IGF - decreased IGF-I SDS, and normal GH peak (n = 160). The relationships among the results of particular tests were evaluated.

Results

In the groups with decreased IGF-I concentrations (GHD Group and low IGF Group), the more severe deficit of height was observed, together with higher TSH and FT₄ but lower FT₃ levels than in groups with normal IGF-I concentrations (ISS Group and low GH Group), independently of the results of GHST. TSH, FT₄ and FT₃ concentrations were - respectively - similar in two groups with decreased IGF-I secretion, as well as in two groups with normal IGF-I levels. Significant correlations were found between patients' height SDS and IGF-I SDS, between FT₃ and IGF-I SDS (positive), and between FT₄ and IGF-I SDS (negative), with no correlation between GH peak and any of the parameters analyzed.

Conclusion

The assessment of thyroid function in children with short stature provides the evidence that measurement of IGF-I concentration may be a procedure reliable at least to the some degree in diagnosing GHD as the results of GHST.

Thyroid function in children with growth hormone (GH) deficiency during the initial phase of GH replacement therapy - clinical implications

Background

Normal thyroid hormone secretion or appropriate L-thyroxine (L-T₄) substitution is necessary for the optimal effect of the growth hormone (GH) administration on growth rate. The decrease of free thyroxine (FT₄) levels at recombinant human GH (rhGH) therapy onset has been reported in several studies. The aim of the present study was to evaluate the effect of rhGH administration on thyrotropin (TSH) and FT₄ serum concentrations in children with GH deficiency (GHD) during the 1st year of therapy, as well as to assess potential indications to thyroid hormone supplementation in them.

Patients and methods

The analysis involved data of 75 children (59 boys, 16 girls) with disorders of GH secretion (GHD, neurosecretory dysfunction - NSD) and partial GH inactivity (inactGH), who were treated with rhGH for - at least - one year. In all the children, body height and height velocity (HV) were assessed before and after 1 year of therapy, while TSH, FT₄, IGF-I and IGFBP-3 before treatment and after 3-6 months and 1 year of treatment. In the patients, who revealed hypothyroidism (HypoT), an appropriate L-T₄ substitution was introduced immediately. The incidence of HypoT, occurring during the initial phase of rhGH therapy, was assessed, as well as its influence on the therapy effectiveness.

Results

Before rhGH substitution, there were no significant differences in either auxological indices or TSH and FT₄ secretion, or IGF-I concentration and its bioavailability among the groups of patients. During the initial 3-6 months of rhGH administration, a significant decrease of FT₄ serum concentration, together with a significant increase of IGF-I SDS and IGF-I/IGFBP-3 molar ratio was observed in all the studied groups. In 17 children, HypoT was diagnosed and L-T₄ substitution was administered. Despite similar IGF-I secretion increase, the improvement of HV presented significantly lower in children with HypoT than in those who remained euthyroid all the time.

Conclusions

The incidence of HypoT during the initial phase of GH treatment in children with GHD and the negative effect of even transient thyroid hormone deficiency on the growth rate should be taken into account.

Growth hormone/insulin-like growth factor axis in patients with subclinical thyroid dysfunction

OBJECTIVE

Our aim was to evaluate serum concentrations of GH, IGF-I, and insulin-like growth factor-binding protein-3 (IGFBP-3) in patients with subclinical thyroid dysfunction before and after normalization of thyroid function.

DESIGN AND METHODS

The study included 51 patients (mean age 42.2+/-1.8 years) with subclinical hypothyroidism and 30 patients (mean age 44.3+/-2.4 years) with subclinical hyperthyroidism. A group of 37 euthyroid healthy subjects were studied as controls. Serum concentrations of TSH, FT4, FT3, GH, insulin, IGF-I, and IGFBP-3 were measured in all patients before starting therapy and after normalization of thyroid function. The dosage of levothyroxine (LT4) and antithyroid drugs was adjusted in attempt to keep the serum-free thyroxine (FT4) and thyrotropin (TSH) concentrations within the normal range.

MAIN OUTCOME

Baseline growth hormone levels were similar with hypothyroid group and hyperthyroid group in relation to euthyroid control subjects. Fasting serum IGF-I levels were significantly lower in the subclinical hypothyroid group compared with the control group. On the other hand, IGF-I levels of subclinical hyperthyroid patients and control group were similar. After normalization of thyroid function tests, IGF-I concentrations were increased in subclinical hypothyroid subjects, but unchanged in subclinical hyperthyroid subjects. Patients with subclinical hyperthyroidism showed slightly lower mean serum IGFBP-3 concentrations than those found in control group, but the difference was not statistically significant. Serum GH and IGFBP-3 levels were unaltered by treatment.

CONCLUSIONS

In this study, it was shown that GH-IGF axis was not affected in patients with subclinical hyperthyroidism, while it was affected in patients with subclinical hypothyroidism. That is, investigation of the axis in subclinical hyperthyroidism would not bring any extra advantages, but LT4 replacement therapy could prevent abnormalities related to GH-IGF axis in patients with subclinical hypothyroidism.

Kidney growth in children with congenital hypothyroidism

The effect of hypothyroidism on kidney size has not been studied in children. The aim of this study was to examine the role of congenital hypothyroidism and levothyroxine (L-thyroxine) treatment on renal growth. Forty children with congenital hypothyroidism and 37 healthy controls were prospectively included. The mean age of patients was 8.2+/-4.7 years. Patients had lower height and weight standard deviation scores compared with controls. The mean L-thyroxine initial age and treatment duration were 37.0 and 60.5 months, respectively. In 62.5% of patients, L-thyroxine was initiated after 6 months of age, and 60.0% of patients had severe hypothyroidism. Patients had lower kidney length and total kidney volume compared with controls (P < 0.05). No significant differences were found in kidney volume/body weight and kidney volume/ body height ratios between patients and controls (P > 0.05). Multiple regression analysis showed significant relationship between relative kidney volume and average free thyroxine level (P < 0.05). No significant differences in kidney sizes were found between patients who had L-thyroxine initiated before and after 6 months of age or between mild/moderate and severe hypothyroidism at diagnosis (P > 0.05). In conclusion, normal renal growth can be accomplished with L-thyroxine replacement despite considerable delay in treatment initiation and/or severe hypothyroidism.

The insulin-like growth axis in patients with autoimmune thyrotoxicosis: effect of antithyroid drug treatment

OBJECTIVE

Hyperthyroidism is associated with altered growth hormone (GH) secretion. Many patients with thyroid dysfunction experience several poorly described complications such as symptoms and signs also seen in patients with growth hormone deficiency (GHD). We have therefore prospectively evaluated a possible relationship between the thyroid function, body composition, leptin levels and insulin-like growth factor (IGF) related peptides in patients with Graves' disease. DESIGN, PATIENTS, AND MEASUREMENTS: In a prospective group of 24 fasting female patients with Graves' disease (mean age (CI 95%): 40 years (33-47)), we measured serum thyroxine, triiodothyronine, thyrotropine (TSH), TSH receptor antibodies, anti-thyroid peroxidase, leptin, body composition, body mass index (BMI) and IGF-related peptides at diagnosis and after 12 months of treatment with thiamazol (ATD).

RESULTS

In thyrotoxic patients IGF-I plus IGF-II correlated positively with IGFBP-3 at baseline (r = 0.90, p < 0.1 x 10(16)) and after 12 months follow-up (r = 0.87, p < 0.1 x 10(-16)). In the thyrotoxic state total IGF-I, IGF-II, IGF binding protein 3 (IGFBP-3) and acid-labile subunit (ALS) but not free IGF-I decreased significantly from 223 microg/L (189-260) (mean (CI 95%), 877 microg/L (801-953), 4165 microg/L (3772-4577) and 22 mg/L (18-26)) to 198 microg/L (172-226), 788 microg/L (711-865), 3431 microg/L (3135-3741) and 19 mg/L (16-26) (p <0.006), respectively, after 12 months of ATD despite an increase in BMI from 22 (21-23) to 23 kg/m(2) (22-25) (p < 0.0004) but no significant changes in leptin.

CONCLUSIONS

The complex IGF systems seemed intact in thyrotoxic patients but change in body composition and the regulation of leptin and insulin secretion during treatment of autoimmune thyroid disease influence IGF-related peptides leaving the patient in a state somewhat similar to partial GHD, but the mechanism behind these alterations remains unclear.

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 hormones play a role in the regulation of insulin-like growth factor type 1 (IGF-1) and insulin-like growth factor-binding protein-3 (IGFBP-3) expression, and both IGF-1 and IGFBPs have been shown to be related to the function and growth of the thyroid. Our aim was to evaluate serum concentrations of IGF-1, IGFBP-1, and IGFBP-3 in patients with thyroid dysfunction before and after normalization of thyroid function. The study was performed in 86 patients with thyroid dysfunction (43 hyperthyroid and 43 hypothyroid patients) and 17 euthyroid subjects. Serum growth hormone (GH), insulin, IGF-1, IGFBP-1, and IGFBP-3 were measured in all patients before and after normalizing serum thyroid hormone concentrations. Hyperthyroid patients showed IGF-1 (198.8 +/- 17.0 microg/L) and IGFBP-3 levels (4.2 +/- 0.2 mg/L) similar to those found in the control group (217.9 +/- 20.3 microg/L and 4.2 +/- 0.3 mg/L, respectively). After therapy these levels significantly decreased to 156.6 + 11.1 microg/L (p < 0.01) and 3.3 +/- 0.1 mg/L (p < 0.001), respectively. IGFBP-1 concentrations were clearly higher than those found in controls (22.7+/- 2.6 vs. 5.7 +/- 1.5 microg/L, p < 0.001) and exhibited a significant reduction after therapy for thyroid hyperfunction (11.0 +/- 1.7 microg/L, p < 0.001). Patients with hypothyroidism showed serum concentrations of IGF-1 (161.5 +/- 13.1 microg/L, p < 0.05) and IGFBP-3 (3.2 +/- 0.3 microg/L, p < 0.05) significantly lower than those found in healthy volunteers. However, replacement therapy with levothyroxine did not induce any significant modification of these concentrations (152.6 +/- 10.6 microg/L and 3.2 +/- 0.2 mg/L, respectively). Similarly, patients with thyroid hypofunction exhibited raised levels of IGFBP-1 (15.5 +/- 0.9 microg/L, p < 0.05 vs. control group) that were significantly decreased after therapy (8.8 +/- 1.4 microg/L, p < 0.01). The results of the present study show that thyroid status affects GH/IGF axis. Hypothyroidism is associated with significant reductions of IGF-1 and IGFBP-3, and IGFBP-1 is elevated in both hypothyroidism and hyperthyroidism.