Comparison between a tubeless, on-body automated insulin delivery system and a tubeless, on-body sensor-augmented pump in type 1 diabetes: a multicentre randomised controlled trial.

AIMS/HYPOTHESIS: This study compares the efficacy and safety of a tubeless, on-body automated insulin delivery (AID) system with that of a tubeless, on-body sensor-augmented pump (SAP). METHODS: This multicentre, parallel-group, RCT was conducted at 13 tertiary medical centres in South Korea. Adults aged 19-69 years with type 1 diabetes who had HbA1c levels of <85.8 mmol/mol (<10.0%) were eligible. The participants were assigned at a 1:1 ratio to receive a tubeless, on-body AID system (intervention group) or a tubeless, on-body SAP (control group) for 12 weeks. Stratified block randomisation was conducted by an independent statistician. Blinding was not possible due to the nature of the intervention. The primary outcome was the percentage of time in range (TIR), blood glucose between 3.9 and 10.0 mmol/l, as measured by continuous glucose monitoring. ANCOVAs were conducted with baseline values and study centres as covariates. RESULTS: A total of 104 participants underwent randomisation, with 53 in the intervention group and 51 in the control group. The mean (±SD) age of the participants was 40±11 years. The mean (±SD) TIR increased from 62.1±17.1% at baseline to 71.5±10.7% over the 12 week trial period in the intervention group and from 64.7±17.0% to 66.9±15.0% in the control group (difference between the adjusted means: 6.5% [95% CI 3.6%, 9.4%], p<0.001). Time below range, time above range, CV and mean glucose levels were also significantly better in the intervention group compared with the control group. HbA1c decreased from 50.9±9.9 mmol/mol (6.8±0.9%) at baseline to 45.9±7.4 mmol/mol (6.4±0.7%) after 12 weeks in the intervention group and from 48.7±9.1 mmol/mol (6.6±0.8%) to 45.7±7.5 mmol/mol (6.3±0.7%) in the control group (difference between the adjusted means: -0.7 mmol/mol [95% CI -2.0, 0.8 mmol/mol] (-0.1% [95% CI -0.2%, 0.1%]), p=0.366). No diabetic ketoacidosis or severe hypoglycaemia events occurred in either group. CONCLUSIONS/INTERPRETATION: The use of a tubeless, on-body AID system was safe and associated with superior glycaemic profiles, including TIR, time below range, time above range and CV, than the use of a tubeless, on-body SAP. TRIAL REGISTRATION: Clinical Research Information Service (CRIS) KCT0008398 FUNDING: The study was funded by a grant from the Korea Medical Device Development Fund supported by the Ministry of Science and ICT; the Ministry of Trade, Industry and Energy; the Ministry of Health and Welfare; and the Ministry of Food and Drug Safety (grant number: RS-2020-KD000056).

Intensity of statin therapy and primary prevention of cardiovascular in Korean patients with dyslipidemia.

This study aimed to investigate the association between the intensity of statin therapy and the development of cardiovascular disease (CVD) and diabetes in individuals without prior diabetes who were being treated for dyslipidemia with statins for the primary prevention of CVD, using the National Health Insurance Service-Health Screening database. The database is a longitudinal cohort study of Korean men and women 40 years of age or older who underwent comprehensive biannual screening health examinations by Korean National Health Insurance Service from January 1, 2002, to December 31, 2015. We included patients in the health screening checkup cohort who underwent health checkups in 2009 and 2010.The primary outcome was the occurrence of a first major cardiovascular or cerebrovascular event, new-onset diabetes. A total of 20,322 participants without prior diabetes at baseline from 2009 to 2015 were followed up for a mean duration of 81.2 ±â€…6.6 months. The mean age of all participants at baseline was 59.2 ±â€…8.4 years and 43.0% of them were male. Their index low lipoprotein cholesterol level was 130.4 ±â€…mg/dL, the mean duration of taking statins was 337.4 ±â€…52.3 days, and 93.9% of them had been taking moderate-intensity statins. At that time, a total of 641 diabetes cases occurred, 41 from using low-intensity statins, 588 from moderate-intensity statins, and 11 from high-intensity statins. The results indicated no significant differences in the incidence of death, CVD death, or CVD among those in the strong statin group compared with the reference groups. While statin treatment for the primary prevention of CVD in patients with dyslipidemia showed a subtle difference in the incidence of diabetes, there was no difference in the occurrence of CVD or CVD death according to statin intensity.

Glucocorticoid-Induced Hyperglycemia: A Neglected Problem.

Glucocorticoids provide a potent therapeutic response and are widely used to treat a variety of diseases, including coronavirus disease 2019 (COVID-19) infection. However, the issue of glucocorticoid-induced hyperglycemia (GIH), which is observed in over one-third of patients treated with glucocorticoids, is often neglected. To improve the clinical course and prognosis of diseases that necessitate glucocorticoid therapy, proper management of GIH is essential. The key pathophysiology of GIH includes systemic insulin resistance, which exacerbates hepatic steatosis and visceral obesity, as well as proteolysis and lipolysis of muscle and adipose tissue, coupled with ß-cell dysfunction. For patients on glucocorticoid therapy, risk stratification should be conducted through a detailed baseline evaluation, and frequent glucose monitoring is recommended to detect the onset of GIH, particularly in high-risk individuals. Patients with confirmed GIH who require treatment should follow an insulin-centered regimen that varies depending on whether they are inpatients or outpatients, as well as the type and dosage of glucocorticoid used. The ideal strategy to maintain normoglycemia while preventing hypoglycemia is to combine basal-bolus insulin and correction doses with a continuous glucose monitoring system. This review focuses on the current understanding and latest evidence concerning GIH, incorporating insights gained from the COVID-19 pandemic.

Adrenalectomy Improves Body Weight, Glucose, and Blood Pressure Control in Patients With Mild Autonomous Cortisol Secretion: Results of an Randomized Controlled Trial by the Co-work of Adrenal Research (COAR) Study.

OBJECTIVE: To assess the metabolic effects of adrenalectomy in patients with mild autonomous cortisol secretion (MACS). BACKGROUND: Despite retrospective studies showing the association of adrenalectomy for MACS with beneficial metabolic effects, there have been only 2 randomized prospective studies with some limitations to date. METHODS: A prospective, multicenter study randomized 132 patients with adrenal incidentaloma without any features of Cushing syndrome but with serum cortisol >50 nmol/L after a 1 mg overnight dexamethasone suppression test into an adrenalectomy group (n = 66) or control group (n = 66). The primary outcomes were changes in body weight, glucose, and blood pressure (BP). RESULTS: Among the 118 participants who completed the study with a median follow-up duration of 48 months (range: 3-66), the adrenalectomy group (n = 46) exhibited a significantly higher frequency of improved weight control, glucose control, and BP control (32.6%, 45.7%, and 45.7%, respectively) compared with the control group (n = 46; 6.5%, P = 0.002; 15.2%, P = 0.002; and 23.9%, P = 0.029, respectively) after matching for age and sex. Adrenalectomy [odds ratio (OR) = 10.38, 95% CI = 2.09-51.52, P = 0.004], body mass index (OR = 1.39, 95% CI = 1.08-1.79, P = 0.010), and cortisol after a 1 mg overnight dexamethasone suppression test levels (OR = 92.21, 95% CI = 5.30-1604.07, P = 0.002) were identified as independent factors associated with improved weight control. Adrenalectomy (OR = 5.30, 95% CI = 1.63-17.25, P = 0.006) and diabetes (OR = 8.05, 95% CI = 2.34-27.65, P = 0.001) were independently associated with improved glucose control. Adrenalectomy (OR = 2.27, 95% CI = 0.87-5.94, P = 0.095) and hypertension (OR = 10.77, 95% CI = 3.65-31.81, P < 0.001) demonstrated associations with improved BP control. CONCLUSIONS: adrenalectomy improved weight, glucose, and BP control in patients with MACS.

Pharmacological Prevention of Ectopic Erythrophagocytosis by Cilostazol Mitigates Ferroptosis in NASH.

Hepatic iron overload (HIO) is a hallmark of nonalcoholic fatty liver disease (NAFLD) with a poor prognosis. Recently, the role of hepatic erythrophagocytosis in NAFLD is emerging as a cause of HIO. We undertook various assays using human NAFLD patient pathology samples and an in vivo nonalcoholic steatohepatitis (NASH) mouse model named STAMTM. To make the in vitro conditions comparable to those of the in vivo NASH model, red blood cells (RBCs) and platelets were suspended and subjected to metabolic and inflammatory stresses. An insert-coculture system, in which activated THP-1 cells and RBCs are separated from HepG2 cells by a porous membrane, was also employed. Through various analyses in this study, the effect of cilostazol was examined. The NAFLD activity score, including steatosis, ballooning degeneration, inflammation, and fibrosis, was increased in STAMTM mice. Importantly, hemolysis occurred in the serum of STAMTM mice. Although cilostazol did not improve lipid or glucose profiles, it ameliorated hepatic steatosis and inflammation in STAMTM mice. Platelets (PLTs) played an important role in increasing erythrophagocytosis in the NASH liver. Upregulated erythrophagocytosis drives cells into ferroptosis, resulting in liver cell death. Cilostazol inhibited the augmentation of PLT and RBC accumulation. Cilostazol prevented the PLT-induced increase in ectopic erythrophagocytosis in in vivo and in vitro NASH models. Cilostazol attenuated ferroptosis of hepatocytes and phagocytosis of RBCs by THP-1 cells. Augmentation of hepatic erythrophagocytosis by activated platelets in NASH exacerbates HIO. Cilostazol prevents ectopic erythrophagocytosis, mitigating HIO-mediated ferroptosis in NASH models.

Intake of Fruit and Glycemic Control in Korean Patients with Diabetes Mellitus Using the Korea National Health and Nutrition Examination Survey.

BACKGRUOUND: Despite the well-recognized health benefits of fresh fruit consumption, there is still substantial uncertainty about its potential effects on glycemic control in patients with type 2 diabetes mellitus (T2DM). METHODS: We examined the association of fresh fruit consumption and glycemic control in patients with T2DM using data from the 6th Korea National Health and Nutrition Examination Survey. The study sample was divided into three groups based on weekly fruit consumption frequency for the analysis. RESULTS: Patients with the highest fruit intake were older than those in the other two groups, and women were more likely to consume fruits in general. Being a current smoker and weekly alcohol intake also showed negative correlations according to the fruit intake tertiles. Fruit consumption was positively correlated with better hemoglobin A1c (HbA1c) levels. Moreover, patients in the highest tertile of fruit intake were 3.48 times more likely to be in good glycemic control defined as HbA1c <7%. CONCLUSION: We observed that fruit consumption can be helpful in glycemic control in Korean patients with T2DM.

Greater Severity of Steatosis Is Associated with a Higher Risk of Incident Diabetes: A Retrospective Longitudinal Study.

BACKGRUOUND: Fatty liver is associated with increased risk of developing type 2 diabetes. We aimed to evaluate whether the severity of hepatic steatosis is associated with incident diabetes. METHODS: We conducted a longitudinal analysis using data from 1,798 participants who underwent a comprehensive health checkup and abdominal computed tomography (CT). We assessed the association between baseline liver attenuation value on non-contrast CT images and risk of incident diabetes. All the participants were categorized into three groups based on the baseline liver attenuation value on non-contrast CT images: without hepatic steatosis (>57 Hounsfield unit [HU]), mild hepatic steatosis (41-57 HU), and moderate to severe hepatic steatosis (≤40 HU). RESULTS: During a median follow-up period of 5 years, 6.0% of the study participants progressed to diabetes. The incidence of diabetes was 17.3% in the moderate to severe hepatic steatosis group, 9.0% in the mild steatosis group, and 2.9% in those without hepatic steatosis. In a multivariate adjustment model, as compared with participants without hepatic steatosis, those with moderate to severe steatosis had a hazard ratio (HR) of 3.24 (95% confidence interval [CI], 1.64 to 4.2) for the development of diabetes, and those in the mild steatosis group had a HR of 2.33 (95% CI, 1.42 to 3.80). One standard deviation decrease in mean CT attenuation values of the liver was associated with a 40% increase in the development of diabetes (multivariate adjusted HR, 1.40; 95% CI, 1.2 to 1.63). CONCLUSION: We found a positive association between severity of hepatic steatosis and risk of incident diabetes. Greater severity of steatosis was associated with a higher risk of incident diabetes.

Adult-Onset Type 1 Diabetes Development Following COVID-19 mRNA Vaccination.

During the coronavirus disease 2019 (COVID-19) pandemic, COVID-19 vaccination-induced hyperglycemia and related complications have been reported. However, there have been few reports of type 1 diabetes triggered by COVID-19 vaccines in subjects without diabetes. Here, we report the case of a 56-year-old female patient who developed hyperglycemia after the second dose of COVID-19 mRNA-based vaccination without a prior history of diabetes. She visited our hospital with uncontrolled hyperglycemia despite administration of oral hyperglycemic agents. Her initial glycated hemoglobin level was high (11.0%), and fasting serum C-peptide level was normal. The fasting serum C-peptide level decreased to 0.269 ng/mL 5 days after admission, and the anti-glutamic acid decarboxylase antibody was positive. The patient was discharged in stable condition with insulin treatment. To our knowledge, this is the first case of the development of type 1 diabetes without diabetic ketoacidosis after mRNA-based COVID-19 vaccination, and is the oldest case of type 1 diabetes development under such circumstances.

Multi-omics analysis revealed TEK and AXIN2 are potential biomarkers in multifocal papillary thyroid cancer.

BACKGROUND: Papillary thyroid carcinoma (PTC), the most common endocrine cancer, accounts for 80-85% of all malignant thyroid tumors. This study focused on identifying targets that affect the multifocality of PTC. In a previous study, we determined 158 mRNAs related to multifocality in BRAF-mutated PTC using The Cancer Genome Atlas. METHODS: We used multi-omics data (miRNAs and mRNAs) to identify the regulatory mechanisms of the investigated mRNAs. miRNA inhibitors were used to determine the relationship between mRNAs and miRNAs. We analyzed the target protein levels in patient sera using ELISA and immunohistochemical staining of patients' tissues. RESULTS: We identified 44 miRNAs that showed a negative correlation with mRNA expression. Using in vitro experiments, we identified four miRNAs that inhibit TEK and/or AXIN2 among the target mRNAs. We also showed that the downregulation of TEK and AXIN2 decreased the proliferation and migration of BRAF ( +) PTC cells. To evaluate the diagnostic ability of multifocal PTC, we examined serum TEK or AXIN2 in unifocal and multifocal PTC patients using ELISA, and showed that the serum TEK in multifocal PTC patients was higher than that in the unifocal PTC patients. The immunohistochemical study showed higher TEK and AXIN2 expression in multifocal PTC than unifocal PTC. CONCLUSIONS: Both TEK and AXIN2 play a potential role in the multifocality of PTC, and serum TEK may be a diagnostic marker for multifocal PTC.

Immune Checkpoint Inhibitors and Endocrine Disorders: A Position Statement from the Korean Endocrine Society.

Immune checkpoint inhibitors (ICIs) including an anti-cytotoxic T-lymphocyte-associated antigen 4 inhibitor, anti-programmed cell death protein 1 (PD-1) inhibitors, and anti-PD-ligand 1 inhibitors are representative therapeutics for various malignancies. In oncology, the application of ICIs is currently expanding to a wider range of malignancies due to their remarkable clinical outcomes. ICIs target immune checkpoints which suppress the activity of T-cells that are specific for tumor antigens, thereby allowing tumor cells to escape the immune response. However, immune checkpoints also play a crucial role in preventing autoimmune reactions. Therefore, ICIs targeting immune checkpoints can trigger various immune-related adverse events (irAEs), especially in endocrine organs. Considering the endocrine organs that are frequently involved, irAEs associated endocrinopathies are frequently life-threatening and have unfavorable clinical implications for patients. However, there are very limited data from large clinical trials that would inform the development of clinical guidelines for patients with irAEs associated endocrinopathies. Considering the current clinical situation, in which the scope and scale of the application of ICIs are increasing, position statements from clinical specialists play an essential role in providing the appropriate recommendations based on both medical evidence and clinical experience. As endocrinologists, we would like to present precautions and recommendations for the management of immune-related endocrine disorders, especially those involving the adrenal, thyroid, and pituitary glands caused by ICIs.

Hedonic Rating of Sucrose Is Sub-Regionally Associated with Striatal Dopamine Transporter in Humans.

BACKGROUND: Eating behavior is determined by both homeostatic and hedonic values. OBJECTIVE: We investigated the association of hedonic value with striatal dopamine transporter (DAT) availability sub-regionally. METHOD: An intravenous bolus injection of 18F-FP-CIT was administered after the infusion of glucose or placebo, and the emission data were acquired over 90 min. DAT availability and binding potential (BPND) were measured via the simplified reference tissue method. Subjects were assessed with sensory taste test of sucrose solutions. The "most liked" sucrose concentration (%) was determined as the hedonic rating for sucrose. RESULTS: Twenty healthy males participated in this study. After glucose loading, BPNDs of putamen significantly increased, and those of caudate nucleus showed the increasing trend, while those of ventral striatum were not significantly different. After glucose loading, the "most liked" sucrose concentration (%) was negatively associated with BPNDs of caudate nucleus and showed the trend of positive association with those from ventral striatum. Slopes of regression lines were significantly different according to the sub-regions of striatum. CONCLUSION: We have highlighted that striatal DAT increased after glucose loading in dorsal striatum, not in ventral striatum. These changes of striatal DAT were sub-regionally associated with the hedonic rating of sucrose from each subject.

Effects of Teneligliptin on HbA1c levels, Continuous Glucose Monitoring-Derived Time in Range and Glycemic Variability in Elderly Patients with T2DM (TEDDY Study).

BACKGROUND: To evaluate the effects of teneligliptin on glycosylated hemoglobin (HbA1c) levels, continuous glucose monitoring (CGM)-derived time in range, and glycemic variability in elderly type 2 diabetes mellitus patients. METHODS: This randomized, double-blinded, placebo-controlled study was conducted in eight centers in Korea (clinical trial registration number: NCT03508323). Sixty-five participants aged ≥65 years, who were treatment-naïve or had been treated with stable doses of metformin, were randomized at a 1:1 ratio to receive 20 mg of teneligliptin (n=35) or placebo (n=30) for 12 weeks. The main endpoints were the changes in HbA1c levels from baseline to week 12, CGM metrics-derived time in range, and glycemic variability. RESULTS: After 12 weeks, a significant reduction (by 0.84%) in HbA1c levels was observed in the teneligliptin group compared to that in the placebo group (by 0.08%), with a between-group least squares mean difference of -0.76% (95% confidence interval [CI], -1.08 to -0.44). The coefficient of variation, standard deviation, and mean amplitude of glycemic excursion significantly decreased in participants treated with teneligliptin as compared to those in the placebo group. Teneligliptin treatment significantly decreased the time spent above 180 or 250 mg/dL, respectively, without increasing the time spent below 70 mg/dL. The mean percentage of time for which glucose levels remained in the 70 to 180 mg/dL time in range (TIR70-180) at week 12 was 82.0%±16.0% in the teneligliptin group, and placebo-adjusted change in TIR70-180 from baseline was 13.3% (95% CI, 6.0 to 20.6). CONCLUSION: Teneligliptin effectively reduced HbA1c levels, time spent above the target range, and glycemic variability, without increasing hypoglycemia in our study population.

Striatal DAT availability does not change after supraphysiological glucose loading dose in humans.

Brain dopamine neurotransmission is regulated by the dopamine transporter (DAT), which drives reuptake of extracellular dopamine into the presynaptic neurons. We hypothesized that the glucose loading dose would affect the striatal DAT availability. An i.v. bolus injection of 18F-FP-CIT was administered after infusion of low-dose glucose (300 mg/kg), high-dose glucose (600 mg/kg) or placebo (normal saline). The emission data were acquired over 90 min in 23 healthy male subjects. Substantial increases of binding potential (BPNDs) from ventral striatum (VST), caudate nucleus, and putamen were observed after low-dose glucose loading (+26.0, +87.0, and +37.8%) and after high-dose glucose loading (+10.4, +51.9, and +22.0%). BPNDs of the caudate nucleus and putamen showed significant differences (P = 0.0472 and 0.0221) after placebo, low-dose glucose, and high-dose glucose loading. BPNDs in the caudate nucleus and putamen after placebo, low-dose glucose, and high-dose glucose loading were positively intercorrelated with each other. In conclusion, striatal DAT changes after physiological glucose loading, but not after supraphysiological glucose loading in humans. DAT availabilities after placebo, low-dose glucose, high-dose glucose loading were correlated to each other in the caudate nucleus and putamen, but not in the VST. Therefore, sub-regional variability in DAT regulatory mechanisms mediated by insulin may exist in humans.

COVID-19 Vaccination for Endocrine Patients: A Position Statement from the Korean Endocrine Society.

Since the first outbreak of coronavirus disease 2019 (COVID-19), ongoing efforts have been made to discover an efficacious vaccine against COVID-19 to combat the pandemic. In most countries, both mRNA and DNA vaccines have been administered, and their side effects have also been reported. The clinical course of COVID-19 and the effects of vaccination against COVID-19 are both influenced by patients' health status and involve a systemic physiological response. In view of the systemic function of endocrine hormones, endocrine disorders themselves and the therapeutics used to treat them can influence the outcomes of vaccination for COVID-19. However, there are very limited data to support the development of clinical guidelines for patients with specific medical backgrounds based on large clinical trials. In the current severe circumstances of the COVID-19 pandemic, position statements made by clinical specialists are essential to provide appropriate recommendations based on both medical evidence and clinical experiences. As endocrinologists, we would like to present the medical background of COVID-19 vaccination, as well as precautions to prevent the side effects of COVID-19 vaccination in patients with specific endocrine disorders, including adrenal insufficiency, diabetes mellitus, osteoporosis, autoimmune thyroid disease, hypogonadism, and pituitary disorders.

Efficacy and Safety of Treatment with Quadruple Oral Hypoglycemic Agents in Uncontrolled Type 2 Diabetes Mellitus: A Multi-Center, Retrospective, Observational Study.

BACKGROUND: Only few studies have shown the efficacy and safety of glucose-control strategies using the quadruple drug combination. Therefore, the aim of the present study was to investigate the usefulness of the quadruple combination therapy with oral hypoglycemic agents (OHAs) in patients with uncontrolled type 2 diabetes mellitus (T2DM). METHODS: From March 2014 to December 2018, data of patients with T2DM, who were treated with quadruple hypoglycemic medications for over 12 months in 11 hospitals in South Korea, were reviewed retrospectively. We compared glycosylated hemoglobin (HbA1c) levels before and 12 months after quadruple treatment with OHAs. The safety, maintenance rate, and therapeutic patterns after failure of the quadruple therapy were also evaluated. RESULTS: In total, 357 patients were enrolled for quadruple OHA therapy, and the baseline HbA1c level was 9.0%±1.3% (74.9±14.1 mmol/mol). After 12 months, 270 patients (75.6%) adhered to the quadruple therapy and HbA1c was significantly reduced from 8.9%±1.2% to 7.8%±1.3% (mean change, -1.1%±1.2%; P<0.001). The number of patients with HbA1c <7% increased significantly from 5 to 68 (P<0.005). In addition, lipid profiles and liver enzyme levels were also improved whereas no changes in body weight. There was no significant safety issue in patients treated with quadruple OHA therapy. CONCLUSION: This study shows the therapeutic efficacy of the quadruple OHA regimen T2DM and demonstrates that it can be an option for the management of T2DM patients who cannot use insulin or reject injectable therapy.

Development and Validation of a Risk Scoring System Derived from Meta-Analyses of Papillary Thyroid Cancer.

BACKGROUND: The aim of this study was to develop a scoring system to stratify the risk of papillary thyroid cancer (PTC) and to select the proper management. METHODS: We performed a systematic search of MEDLINE and Embase. Data regarding patients' prognoses were obtained from the included studies. Odds ratios (ORs) with statistical significance were extracted from the publications. To generate a risk scoring system (RSS), ORs were summed (RSS1), and summed after natural-logarithmic transformation (RSS2). RSS1 and RSS2 were compared to the eighth edition of the American Joint Committee on Cancer (AJCC) staging system and the 2015 American Thyroid Association (ATA) guidelines for thyroid nodules and differentiated thyroid carcinoma. RESULTS: Five meta-analyses were eligible for inclusion in the study. Eight variables (sex, tumour size, extrathyroidal extension, BRAF mutation, TERT mutation, histologic subtype, lymph node metastasis, and distant metastasis) were included. RSS1 was the best of the analysed models. CONCLUSION: We developed and validated a new RSS derived from previous meta-analyses for patients with PTC. This RSS seems to be superior to previously published systems.

Hepatic STAMP2 mediates recombinant FGF21-induced improvement of hepatic iron overload in nonalcoholic fatty liver disease.

Although previous studies have shown that the administration of fibroblast growth factor 21 (FGF21) reverses hepatic steatosis, the mechanism by which FGF21 exerts a therapeutic effect on nonalcoholic fatty liver disease (NAFLD) is not yet entirely understood. We previously demonstrated that hepatic six transmembrane protein of prostate 2 (STAMP2) may represent a suitable target for NAFLD. We investigated the mechanism underlying the therapeutic effect of recombinant FGF21 on NAFLD, focusing on the involvement of hepatic STAMP2. In this study, we used human nonalcoholic steatosis patient pathology samples, C57BL/6 mice for a high-fat diet (HFD)-induced in vivo NAFLD model, and used human primary hepatocytes and HepG2 cells for oleic acid (OA)-induced in vitro NAFLD model. We observed that recombinant FGF21 treatment ameliorated hepatic steatosis and insulin resistance through the upregulation of STAMP2 expression. We further observed hepatic iron overload (HIO) and reduced iron exporter, ferroportin expression in the liver samples obtained from human NAFLD patients, and HFD-induced NAFLD mice and in OA-treated HepG2 cells. Importantly, recombinant FGF21 improved HIO through the hepatic STAMP2-mediated upregulation of ferroportin expression. Our data suggest that hepatic STAMP2 may represent a suitable therapeutic intervention target for FGF21-induced improvement of NAFLD accompanying HIO.