Introduction: Accurate diagnosis of thyrotoxicosis, a condition resulting from excessive thyroid hormone activity, is essential for appropriate management. However, access to diagnostic tools such as thyrotropin receptor antibody (TRAb) assays and thyroid ultrasonography remains limited in resource-constrained settings, highlighting the need for cost-effective alternatives. Recent studies suggest that the free triiodothyronine to free thyroxine (FT3/FT4) ratio may serve as a potential biomarker for differentiating the causes of thyrotoxicosis. Methodology: This cross-sectional study evaluated the FT3/FT4 ratio in newly diagnosed thyrotoxicosis patients aged ≥18 years recruited from Hospital Tengku Ampuan Rahimah, Hospital Banting, Klinik Kesihatan Pelabuhan Klang, and Klinik Kesihatan Pandamaran between February and December 2025. All participants underwent thyroid function testing (FT3, FT4, and TSH) and autoantibody assessment (TRAb and anti-thyroid peroxidase [anti-TPO]). Diagnostic performance of the FT3/FT4 ratio for Graves’ disease was assessed using receiver operating characteristic (ROC) curve analysis. Results: Fifty-eight patients were included, of whom 58.6% were diagnosed with Graves’ disease. Patients with Graves’ disease had significantly higher FT3 levels (median 16.8 pmol/L; IQR 10.9–25.7) compared to those with non-Graves’ thyrotoxicosis (median 8.3 pmol/L; IQR 5.3–13.5; p <0.001), with similar trends observed for FT4 levels (p <0.001). However, the FT3/ FT4 ratio did not differ significantly between groups (p >0.05), with an overall ROC AUC of 0.572, indicating poor discriminatory ability. Subgroup analysis based on FT4 levels improved performance; at FT4 <30 pmol/L, the FT3/FT4 ratio demonstrated 75.0% sensitivity, 91.7% specificity, and 87.5% diagnostic accuracy at a cutoff of 0.3445 (AUC = 0.813; 95% CI: 0.570–1.000; p = 0.069). No significant association was observed between the FT3/FT4 ratio and TRAb or anti-TPO. Conclusion The FT3/FT4 ratio has limited overall diagnostic utility but may provide adjunctive value in selected biochemical contexts, particularly in settings with limited access to immunological testing.
Diagnosis, Differential ; Thyroxine ; Triiodothyronine ; Thyrotoxicosis ; Cross-Sectional Studies

Introduction: Thyroid stimulating hormone (TSH) suppression following differentiated thyroid carcinoma is widely recommended to reduce recurrence risk. However, this strategy assumes cardiovascular tolerance to supraphysiologic thyroid hormone exposure. In patients with advanced structural heart disease, this assumption may fail, exposing a critical limitation of guideline-directed TSH suppression. Case: We report a 71-year-old male with end-stage renal failure on hemodialysis and severe ischemic cardiomyopathy (ejection fraction 23%) who presented with acute decompensation characterized by dyspnea, rapid atrial fibrillation, and non–ST-elevation myocardial infarction. He had a history of papillary thyroid carcinoma treated with total thyroidectomy and radioactive iodine over 20 years prior and was maintained on levothyroxine 200 mcg daily for TSH suppression. Despite biochemically euthyroid indices (TSH 1.8 mIU/L, free thyroxine 4 17 pmol/L), he developed recurrent arrhythmia with heart failure decompensation. This case highlights a dissociation between biochemical euthyroidism and tissue-level thyrotoxicity in a structurally compromised myocardium. Papillary thyroid carcinoma after definitive therapy typically follows an indolent course with low short-term mortality. In contrast, in severe left ventricular dysfunction, excess thyroid hormone increases adrenergic sensitivity and myocardial oxygen demand, precipitating arrhythmia and ischemia. This risk is amplified in end-stage renal disease, where altered hormone handling renders biochemical indices less reliable. Conclusion Biochemical euthyroidism does not equate to physiological safety. In patients with advanced cardiovascular disease, thyroid hormone therapy should be titrated to cardiovascular tolerance rather than oncologic targets alone, and routine TSH suppression may be inappropriate.
Thyroxine ; Heart Failure ; Thyrotropin

OBJECTIVE: By analyzing the hormone secretion of the adenohypophysis, thyroid glands, gonads, and adrenal cortex in patients with hematological diseases before and after hematopoietic stem cell transplantation (HSCT), this study aims to preliminarily explore the effect of HSCT on patients' hormone secretion and glandular damage. METHODS: The baseline data of 209 hematological disease patients who underwent HSCT in our hospital from January 2019 to December 2023, as well as the data on the levels of hormones secreted by the adenohypophysis, thyroid glands, gonads and adrenal cortex before and after HSCT were collected, and the changes in hormone levels before and after transplantation were analyzed. RESULTS: After allogeneic HSCT, the levels of thyroid-stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (FT3) and estradiol (E2) decreased, while the levels of luteinizing hormone (LH) and follicle- stimulating hormone (FSH) increased. The T3 level of patients with decreased TSH after transplantation was lower than that of those with increased TSH after transplantation. In female patients, the levels of prolactin (PRL), progesterone (Prog), and testosterone (Testo) decreased after HSCT. Testo and PRL decreased when there was a donor-recipient sex mismatch, and the levels of adrenocorticotropic hormone (ACTH) and cortisol (COR) decreased when the HLA matching was haploidentical. The levels of T3, FT3, and PRL decreased after autologous HSCT. In allogeneic HSCT patients, the levels of TSH, T4, T3, FT3, and ACTH in the group with graft-versus-host disease (GVHD) were significantly lower than those in the group without GVHD. Logistic regression analysis showed the changes in hormone levels after transplantation were not correlated with factors such as the patient's sex, age, or whether the blood types of the donor and the recipient are the same. CONCLUSION HSCT can affect the endocrine function of patients with hematological diseases, mainly affecting target glandular organs such as the thyroid, gonads, and adrenal glands, while the secretory function of the adenohypophysis is less affected.
Humans ; Hematopoietic Stem Cell Transplantation ; Female ; Male ; Hematologic Diseases/blood* ; Follicle Stimulating Hormone/blood* ; Triiodothyronine/blood* ; Luteinizing Hormone/blood* ; Thyroid Gland/metabolism* ; Estradiol/blood* ; Thyrotropin/blood* ; Gonads/metabolism* ; Adult ; Middle Aged ; Adrenocorticotropic Hormone/blood* ; Hormones/metabolism* ; Adrenal Cortex/metabolism* ; Prolactin

BACKGROUND: Subclinical hypothyroidism (SCH) has been reported to be associated with lower endothelial progenitor (CD34-positive) cell count, whereas an inverse association between circulating CD34-positive cell count and height loss is documented. Reports indicate height loss to be associated with all-cause mortality, and a higher CD34-positive cell count has been shown to predict longer life. Therefore, evaluating the association between SCH and height loss provides mechanistic insights underlying the association between height loss and mortality risk. METHODS: A prospective study involving 1,599 participants with normal free triiodothyronine (T3) and free thyroxine (T4) levels was conducted to determine the association between SCH and height loss.Since the free T4 level influences the supply of active thyroid hormone (free T3), the analysis was stratified by the median free T4 level. Height loss was defined as the highest quintile of annual height decrease. RESULTS: SCH was positively associated with height loss in participants with low-normal free T4 levels (below the median), but not in those with high-normal free T4 levels (at or above the median). After adjusting for sex, age, free T3 level, atherosclerosis, and known cardiovascular risk factors, the adjusted odds ratios (95% confidence interval) for height loss were 1.88 (1.02, 3.47) and 1.92 (1.02, 3.62) in the low-normal free T4 group. The corresponding values in the high-normal free T4 group were 0.37 (0.08, 1.69) and 0.43 (0.09, 1.97). CONCLUSION SCH could influence height loss, and free T4 might influence the association between SCH and height loss in euthyroid individuals. These results clarify the mechanisms underlying the association between height loss and mortality risk.
Humans ; Hypothyroidism/epidemiology* ; Thyroxine/blood* ; Male ; Female ; Prospective Studies ; Middle Aged ; Body Height ; Adult ; Aged ; Risk Factors

Objective: To investigate the association between triiodothyronine (T₃) and inflammatory factors, and its potential effect on long-term outcomes in hospitalized patients with heart failure (HF). Methods: A total of 2 475 patients with HF admitted in Heart Failure Care Unit were consecutively enrolled in this retrospective cohort study from December 2006 to June 2018. Patients were divided into low T₃ syndrome group (n=610, 24.6%) and normal thyroid function group (n=1 865, 75.4%). The median follow-up time was 2.9 (1.0, 5.0) years. A total of 1 048 all-cause deaths were recorded at the final follow-up. The effects of free T₃ (FT₃) and high-sensitivity C-reactive protein (hsCRP) on the risk of all-cause death were evaluated by Cox regression analysis and Kaplan-Meier analysis. Results: The age of the total population was 19-95 (57±16) years, 1 823 cases (73.7%) were male. Compared to those with normal thyroid function, albumin [(36.5±5.4) vs. (40.7±4.7) g/L], hemoglobin [(129.4±25.1) vs. (140.6±20.6) g/L], total cholesterol [3.6 (3.0, 4.4) vs. 4.2 (3.5, 4.9) mmol/L] (all P<0.001) were lower, Whereas age [(60.5±16.0) vs. (55.2±15.4) years], creatinine [105.0 (83.6, 137.0) vs. 87.8 (75.6, 106.3) mmol/L], log N-terminal B-type natriuretic peptide [(8.2±1.3) vs. (7.2±1.4) ng/L] were higher in LT₃S patients (all P<0.001). In Kaplan-Meier survival analysis, patients with lower FT₃ and higher hsCRP had significantly lower cumulative survival (P<0.001), lower FT₃ combined with higher hsCRP subgroup had the highest risk of all-cause death (P_trend<0.001). In multivariate Cox regression analysis, LT₃S was an independent predictor of all-cause mortality (HR=1.40, 95%CI 1.16-1.69, P<0.001). Conclusion: LT₃S is an independent predictor of poor prognosis in patients with heart failure. FT₃ combined with hsCRP improve the predictive value of all-cause death in hospitalized patients with heart failure.
Humans ; Male ; Young Adult ; Adult ; Middle Aged ; Aged ; Aged, 80 and over ; Female ; C-Reactive Protein ; Retrospective Studies ; Heart Failure ; Prognosis ; Triiodothyronine ; Syndrome

Objective: To investigate the risk factors of childhood systemic lupus erythematosus (SLE) with thyroid dysfunction and to explore the relationship between thyroid hormone and kidney injury of lupus nephritis (LN). Methods: In this retrospective study, 253 patients who were diagnosed with childhood SLE and hospitalized in the First Affiliated Hospital of Zhengzhou University from January 2019 to January 2021 were enrolled in the case group, and 70 healthy children were the control cases. The patients in the case group were divided into the normal thyroid group and the thyroid dysfunction group. Independent t-test, χ² test, and Mann-Whitney U test were used for comparison between the groups, Logistic regression analysis was used for multivariate analysis, and Spearman correlation. Results: A total of 253 patients, there were 44 males and 209 females in the case group, and the age of onset was 14 (12, 16) years; a total of 70 patients, 24 males and 46 females were in the control group, and the age of onset was 13 (10, 13) years. The incidence of thyroid dysfunction in the case group was higher than that in the control group (48.2% (122/253) vs. 8.6% (6/70), χ²=36.03, P<0.05). Of the 131 patients, there were 17 males and 114 females in the normal thyroid group, and the age of onset was 14 (12, 16) years. Of the 122 patients in the thyroid dysfunction group, 28 males and 94 females were in the thyroid dysfunction group, and the age of onset was 14 (12, 16) years. Of the 122 had thyroid dysfunction, including 51 cases (41.8%) with euthyroid sick syndrome, 25 cases (20.5%) with subclinical hypothyroidism, 18 cases (14.8%) patients with sub-hyperthyroidism, 12 cases (9.8%) with hypothyroidism, 10 cases (8.2%) with Hashimoto's thyroiditis, 4 cases (3.3%) with hyperthyroidism, and 2 cases (1.6%) with Graves disease. Compared to patients with normal thyroid function, the serum level of triglyceride, total cholesterol, urine white blood cell, urine red blood cell, 24 h urine protein, D-dimer, and fibrinogen, ferritin and systemic lupus erythematosus disease activity Index-2000 (SLEDAI-2K) score were higher in patients with thyroid dysfunction (Z=3.07, 3.07, 2.48, 3.16, 2.40, 3.99, 2.68, 2.55, 2.80, all P<0.05), while the serum level of free thyroxine and C3 were lower in thyroid disfunction patients (10.6 (9.1, 12.7) vs. 11.3 (10.0, 12.9) pmol/L, and 0.46 (0.27, 0.74) vs. 0.57 (0.37, 0.82) g/L, Z=2.18, 2.42, both P<0.05). The higher level of triglyceride and D-dimer were the independent risk factors for childhood SLE with thyroid dysfunction (OR=1.40 and 1.35, 95%CI 1.03-1.89 and 1.00-1.81, respectively, both P<0.05). There were 161 patients with LN in the case group, all of which were conducted with renal biopsies, including 11 cases (6.8%) with types Ⅰ LN, 11 cases (6.8%) with typesⅡLN, 31 cases (19.3%) with types Ⅲ LN, 92 cases (57.1%) with types Ⅳ LN, and 16 cases (9.9%) with types Ⅴ LN. There were significant differences in the level of free triiodothyronine and thyroid stimulating hormone among different types of kidney pathology (both P<0.05); compared with types I LN, the serum level of free triiodothyronine was lower in types Ⅳ LN (3.4 (2.8, 3.9) vs. 4.3 (3.7, 5.5) pmol/L, Z=3.75, P<0.05). The serum level of free triiodothyronine was negatively correlated with the acute activity index score of lupus nephritis (r=-0.228, P<0.05), while the serum level of thyroid stimulating hormone was positively correlated with the renal pathological acute activity index score of lupus nephritis (r=0.257, P<0.05). Conclusions: There is a high incidence of thyroid dysfunction in childhood SLE patients. The higher SLEDAI and more severe renal damage were found in SLE patients with thyroid dysfunction compared to these with normal thyroid functions. The risk factors of childhood SLE with thyroid dysfunction are the higher level of triglyceride and D-dimer. The serum level of thyroid hormone is possibly related to the kidney injury of LN.
Child ; Female ; Male ; Humans ; Lupus Nephritis/epidemiology* ; Triiodothyronine ; Retrospective Studies ; Lupus Erythematosus, Systemic/complications* ; Hypothyroidism/epidemiology* ; Hyperthyroidism ; Risk Factors

BACKGROUND: More than 75 million procedures with intravascular iodine-based contrast media (ICM) are performed worldwide every year, and some patients undergoing these procedures do not have normal thyroid function. The long-term effects of ICM in patients with mild thyroid dysfunction (TD) are unclear. METHODS: This prospective cohort study was conducted in China. Patients with stable angina pectoris with total triiodothyronine (TT3) reduction, normal thyroid-stimulating hormone, and reverse triiodothyronine (rT3) were enrolled and divided into high-dose (≥100 mL ICM) and low-dose groups (<100 mL ICM). We dynamically investigated the trends in thyroid function, rT3, and thyroid antibodies one year after ICM exposure. RESULTS: A total of 154 patients completed 6 months of follow-up and 149 completed 1 year of follow-up. Thyroglobulin antibody (TGAB) levels were elevated in 41 (26.6%) patients before ICM exposure, 11 (7.1%) of whom also had elevated thyroid peroxidase antibody levels. Transient subclinical TD occurred 6 months after ICM exposure; 75.5% (34/45) of post-operative TD occurred in the high-dose group. One patient developed severe hypothyroidism with myxedema, requiring drug intervention 1 year after ICM exposure. The level of rT3 showed no statistically significant changes during post-operative follow-up ( P  = 0.848). The TGAB level decreased at 6th month ( P  < 0.001), but increased at 1 year after ICM exposure ( P  = 0.002). CONCLUSIONS Patients with T3 reduction are at a risk of transient subclinical TD and hypothyroidism after a single large dose of ICM. Follow-up of this population at 9-12 months after ICM exposure is warranted.
Humans ; Contrast Media/adverse effects* ; Prospective Studies ; Hypothyroidism ; Triiodothyronine ; Iodine/adverse effects* ; Thyrotropin ; Thyroxine

OBJECTIVE: To assess the influence of thyroid function on the fetal fraction (FF) during the second trimester of pregnancy. METHODS: A total of 1 861 pregnant women undergoing non-invasive prenatal testing (NIPT) and thyroxine function testing at 12 ~ 26 gestational weeks at the Affiliated Suzhou Hospital of Nanjing Medical University/Suzhou Municipal Hospital from January 2016 to December 2020 were selected as the study subjects. Univariate analysis and multivariate regression models were used to assess the correlation between free thyroxine 4 (FT4) levels and FF. RESULTS: Univariate linear regression analysis indicated that the FF is correlated to the level of FT4 (b = 0.035, P < 0.001). The median fetal FF was 10.78% (IQR: 8.2%, 13.82%), and this has increased along with the level of FT4 from 10.58% at <= 12.0 pmol/L to 11.77% at > 16.0 pmol/L. After further adjustment of gestational age and body mass index (BMI), the FF showed an increase trend along with the increase of FT4 levels, and a trend test also showed a statistical significance (Ptrend < 0.001). CONCLUSION Maternal FF can be affected by the level of free thyroxine during the second trimester of pregnancy.
Pregnancy ; Female ; Humans ; Pregnancy Trimester, Second ; Thyroid Gland ; Thyroxine ; Fetus ; Gestational Age

Thyroid hormone plays an important role in cardiovascular function. Pericardial effusions are commonly seen in cases of severe hypothyroidism. However, large to massive pericardial effusions with cardiac tamponade are exceptionally rare. Herein, we present two cases of severe hypothyroidism with massive pericardial effusion. Our first case demonstrates that a patient with large pericardial effusion can be managed conservatively with aggressive thyroid hormone replacement therapy. In our second case, pericardiocentesis was performed in addition to thyroid hormone replacement therapy as the underlying aetiology of effusion could not be reasonably limited to hypothyroidism. These two cases served to highlight and demonstrate rapid normalisation of thyroid function test by using aggressive oral thyroid hormone replacement therapy using liothyronine, in combination with levothyroxine, which led to resolution of pericardial effusion and prevent its re-accumulation.
Pericardial Effusion ; Thyroxine ; Triiodothyronine

Objective: To investigate the effect of low-dose X-ray ionizing radiation on thyroid function of radiation workers. Methods: From January to December 2021, a total of 1039 medical workers in some tertiary hospitals in Wuhan were selected as the survey subjects, of which 518 radiation workers were selected as the exposure group, and 521 non-radiation workers were selected as the control group. The general conditions of the two groups were collected, and 5 indicators of thyroid function were measured, including total thyroxine (TT(4)) , total triiodothyronine (TT(3)) , free triiodothyronine (FT(3)) , thyroid stimulating hormone (TSH) , and free thyroxine (FT(4)) . The annual cumulative dose of ionizing radiation exposure in the exposure group was collected. Pearson χ(2) test and independent sample t test were used to compare the general conditions, 5 indicators of thyroid function and abnormal rate between the two groups. Linear regression model was used to analyze the correlation between the annual cumulative dose and 5 indicators of thyroid function in the exposure group. Binary logistic regression was used to analyze the influencing factors of thyroid dysfunction in the exposure group. Results: The TT(4) levels of the workers in the control group and the exposure group were (7.95±1.07) μg/dl and (8.26±1.41) μg/dl, respectively, and the FT(4) levels were (16.33±2.19) pmol/L and (17.15±2.42) pmol/L, respectively, the rate of thyroid dysfunction was 4.80% (25/521) and 8.49% (44/518) , and the above differences were statistically significant (P<0.05) . Linear regression analysis showed that the annual cumulative dose of the exposure group was significantly correlated with TT(4), TT(3), FT(4), and TSH (P<0.05) . For every 1 mSv increase in the annual cumulative dose, TT(4) increased by 1.661 μg/dl, FT(4) increased by 1.422 pmol/L, TT(3) decreased by 0.113 ng/ml, and TSH decreased by 0.731 μIU/ml. Binary logistic regression analysis showed that the older the radiation workers, the higher the risk of thyroid dysfunction (OR=1.080, 95% CI: 1.016-1.148, P=0.013) ; the greater the annual cumulative dose, the higher the risk of thyroid dysfunction (OR=6.400, 95%CI: 1.796-22.811, P=0.004) . Conclusion: The annual cumulative dose of low-dose X-ray ionizing radiation is positively correlated with thyroid function TT(4) and FT(4) of radiation workers, and negatively correlated with TT(3) and TSH; the greater the age and annual cumulative dose, the higher the risk of thyroid dysfunction.
Humans ; Triiodothyronine ; Thyroxine ; Thyroid Gland/radiation effects* ; X-Rays ; Thyrotropin ; Radiation, Ionizing