The hepcidin concentration decreases in hypothyroid patients with Hashimoto's thyroiditis following restoration of euthyroidism

Relationship between Iron Deficiency and Thyroid Function: A Systematic Review and Meta-Analysis

Objective: Iron deficiency (ID) is the most prevalent nutritional deficiency worldwide. Low levels of serum ferritin (SF) could affect the thyroid gland and its functioning. The purpose of this systematic review and meta-analysis is to summarize the main currently available evidence and analyze data on the relationship between ID and thyroid function. Methods: This study included all articles evaluating the relationship between ID and thyroid function. Quality assessment was performed using Cambridge Quality Checklists. The search strategy included the following combination of Medical Subjects Headings terms and keywords: "iron deficiency", "thyroid function", "thyroid disease", "thyroid dysfunction", and "hypothyroidism". A meta-analysis was performed to evaluate whether thyroid stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels differed between patients with ID and healthy controls without ID. For statistical comparison between cases and controls, the mean difference (MD) was calculated, and a subgroup analysis of pregnant and non-pregnant women was performed. Cochran's Q testing and heterogeneity indices (I2) were used to assess statistical heterogeneity. Sensitivity analysis and publication bias analyses were also performed, both qualitatively and quantitatively. Finally, a meta-regression analysis was performed to evaluate the correlation between serum TSH or FT4 levels and SF in the study population. Results: Ten cross-sectional studies were identified and reviewed. Patients with ID showed TSH (MD: -0.24 mIU/L; 95% CI -0.41, -0.07; I2 = 100%, p = 0.005), FT4 (MD: -1.18 pmol/L; 95% CI -1.43, -0.94; I2 = 99%, p < 0.000001), and FT3 (MD: -0.22 pmol/L; 95% CI -0.32, -0.12; I2 = 99%, p < 0.00001) levels that were significantly lower. Subgroup analysis confirmed significantly lower TSH, FT4, and FT3 levels in pregnant women. Non-pregnant women showed significantly lower serum FT4 and FT3 levels but no difference in TSH values. Meta-regression analysis showed that serum TSH and FT4 levels were positively correlated with SF levels. Our systematic review of the literature found that ID significantly increases the prevalence of thyroid autoantibody (anti-thyroglobulin antibodies and anti-thyroid peroxidase antibodies) positivity both individually and collectively. Conclusion: Studies currently published in the literature indicate a possible relationship between ID, thyroid function, and autoimmunity, especially in some patient groups. Data analysis shows that thyroid hormone levels are lower in patients with ID and, in particular, in pregnant women. Further studies are needed to understand the role played by iron in thyroid metabolism.

Impact of thyroid hormone treatment on maternal pregnancy outcomes in women with subclinical hypothyroidism without TPOAb: a retrospective cross-sectional study

BACKGROUND

Evidence on the impact of thyroid hormone treatment (LT4) on maternal pregnancy outcomes in women with subclinical hypothyroidism (SCH) without thyroid peroxidase antibodies (TPOAb) positivity is scarce.

METHODS

Single centre, cross-sectional study in 1460 women screened for TSH, free T4 and TPOAb at median 13 (11-17) weeks of gestation during the period 2013-2014. Exclusion criteria were twin- and assisted reproduction pregnancies, TPO positivity, overt thyroid dysfunction, and treatment with LT4 before screening. The impact of LT4 on maternal pregnancy outcomes was investigated in a group of 53 women with SCH (TSH > 3.74 mIU/L) in which LT4 was initiated at median 13 (10-22) weeks (treated group). The control group included 18 women with SCH (TSH > 3.74 mIU/L). The prevalence of pregnancy complications in these two groups was compared with that in a euthyroid reference (REF) group of 1389 women (TSH ≤ 3.74 mIU/L).

RESULTS

The prevalence of pre-eclampsia and gestational diabetes (GDM) was higher in the control group vs the REF group (16.7% vs 5.0% and 27.8% vs 18.9%; p = 0.017 and p = 0.016, respectively), but comparable in the treated group vs the REF group (7.6% vs 5.0% and 22.6% vs 18.9%; p = 0.918 and 0.676, respectively). The prevalence of iron-deficiency anaemia was lower in the treated vs the REF group (17.0% vs 32.5%; p = 0.017).

CONCLUSION

Pregnant women with untreated SCH and without TPOAb positivity had a higher prevalence of pre-eclampsia and GDM compared with euthyroid women, while this was not the case in women with treated SCH, even when it was initiated after the first trimester.

Iron Homeostasis and Hepcidin Concentration in Patients With Acromegaly

Hepcidin is a protein responsible for maintaining iron (Fe) homeostasis. Data regarding the role of hepcidin in the pathomechanism of Fe balance disturbances associated with acromegaly (AG) are scarce. The aim of the study was to assess the impact of alterations in complete blood count parameters, Fe homeostasis, gonadal status and GH/IGF-1 on the level of hepcidin in AG patients. The study evaluated the differences in hepcidin concentration and iron homeostasis between patients newly diagnosed with AG in comparison to healthy control subjects (CS). We prospectively enrolled 25 adult patients newly diagnosed with AG and 25 healthy volunteers who served as CS. The level of hepcidin was measured using the Hepcidin 25 (bioactive) hs ELISA, which is a highly sensitive enzyme immunoassay for the quantitative in vitro diagnostic measurement (DRG Instruments GmbH, Germany). The median of hepcidin concentration in the serum of patients with AG was significantly lower 9.8 (6.2-18.2) ng/ml as compared to CS 21.3 (14.3-34.0) ng/ml (p = 0.003). In the AG group, a statistically significant negative correlation between hepcidin and IGF-1 (rho = -0.441) was observed. Our study demonstrated a decreased hepcidin level in AG patients in comparison to CS what may have a potentially protective effect against anemia through an increased bioavailability of Fe. Additionally, GH may have a positive direct or indirect effect on erythropoiesis. Further studies on larger patient groups are necessary in order to clarify the exact role of hepcidin in the regulation of erythropoiesis in the excess of GH/IGF-1.

Changes in serum hepcidin according to thyrometabolic status in patients with Graves' disease

INTRODUCTION

Hepcidin is an acute-phase protein and a key regulator of iron homeostasis. Anaemia frequently occurs in patients with thyroid dysfunction, and hepcidin may be a potential link.

OBJECTIVES

Prospective assessment of hepcidin serum concentration and other parameters related to Fe homeostasis in hyperthyroid patients in the course of GD at diagnosis and during remission.

PATIENTS AND METHODS

Out of 70 patients recruited, 42 (32 women, 10 men), aged 42.5±15.1 years, met the inclusion criteria. Clinical and biochemical assessment, including hepcidin measurement by ELISA, was performed at baseline (T0) and after restoration of euthyroidism (T1).

RESULTS

Hepcidin concentration at T0 in the 24 patients who completed the study was significantly higher than the value during euthyroidism (28.7 (8.1-39.4) ng/mL vs. 7.9 (4.3-12.9) ng/mL, p<0.001). Hepcidin level was most significantly correlated with ferritin (rho = 0.723) in women at T0. In both men (377 (171-411) vs. 165 (84-237) ng/mL, p=0.001) and women (84 (23-104) vs. 35 (16-64) ng/mL, p=0.001), a significant decrease in ferritin level was demonstrated following therapy. A significant (p<0.001) increase in mean corpuscular volume (MCV) (83.5 (82.5-87.1) vs. 89.5 (88.8-90.0) fL) and mean concentration of haemoglobin (MCH) (29.0 (28.0-29.4) vs. 30.4 (29.5-31.1) pg) was observed.

CONCLUSIONS

Hepcidin and ferritin decrease significantly during the transition from a hyperthyroid state to euthyroidism in patients with GD. The observed changes occur in parallel to iron homeostasis fluctuations. During the transition from the hyperthyroid state to euthyroidism, the improvement of haematological status is reflected mainly by the increase in MCV and MCH.