Effects of Chronic Suppression or Oversuppression of Thyroid-Stimulating Hormone on Psychological Symptoms and Sleep Quality in Patients with Differentiated Thyroid Cancer.

In differentiated thyroid cancer (DTC), the standard treatment includes total thyroidectomy and lifetime levothyroxine (LT4) replacement. However, long-term exogenous LT4 has become controversial due to the adverse effects of oversuppression. The study included 191 patients (aged 18-76 years) with a prospective diagnosis of non-metastatic DTC and 79 healthy individuals. The patients with DTC were stratified into three groups according to their TSH levels: suppressed thyrotropin if TSH was below 0.1 µIU/ml, mildly suppressed thyrotropin if TSH was between 0.11 and 0.49 µIU/ml, and low-normal thyrotropin if THS was between 0.5 and 2 µIU/ml. The Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Anxiety Sensitivity Index (ASI), Short Symptom Inventory (SSI), and Pittsburgh Sleep Quality Index (PSQI) were administered to all participants. It was found that the BDI, BAI, SSI and PSQI scores were worse in patients with DTC (p=0.024, p=0.014, p=0.012, and p=0.001, respectively). According to theTSH levels, the mean ASI was found to be higher in the suppressed and mildly suppressed thyrotropin groups (19±14.4 vs. 10.6±11.1; 16.4±14.9 vs. 10.6±11.1, p=0.024, respectively), the mean SSI was found higher in the suppressed group (61.0±55.5 vs. 35.1±37.0, p=0.046), and the mean PSQI was higher in all three groups (7.94±3.97 vs. 5.35±4.13; 7.21±4.59 vs. 5.35±4.13; 7.13±4.62 vs. 5.35±4.13, p=0.006) when compared with the controls. No significant difference was found between the groups. A positive correlation was detected in the duration of LT4 use and BDI and SSI, and a weak, negative correlation was detected between TSH levels and ASI and PSQI. Based on our study, it was found that depression, anxiety disorders, and sleep problems were more prevalent in patients with DTC, being more prominent in the suppressed TSH group. These results were inversely correlated with TSH values and positively correlated with the duration of LT4 use. Unnecessary LT4 oversuppression should be avoided in patients with DTC.

The impact of levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity in men with autoimmune hypothyroidism and early-onset androgenetic alopecia.

INTRODUCTION: Administration of testosterone or dehydroepiandrosterone to subjects with low levels of these hormones was found to reduce thyroid antibody titres. Male-pattern baldness is accompanied by mildly increased androgen levels. The present study was aimed at investigating whether early-onset androgenetic alopecia determines the impact of exogenous levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity in young men with autoimmune hypothyroidism. MATERIAL AND METHODS: The study included 2 thyroid-antibody-matched groups of men with autoimmune hypothyroidism: subjects with early-onset androgenetic alopecia (group 1; n = 24) and subjects with no evidence of hair loss (group 2; n = 24). All patients were treated with exogenous levothyroxine. Circulating titres of thyroid peroxidase and thyroglobulin antibodies, as well as levels of thyrotropin, free thyroxine, free triiodothyronine, prolactin, total testosterone, calculated bioavailable testosterone, dehydroepiandrosterone-sulphate, and oestradiol were measured before levothyroxine treatment and 6 months later. RESULTS: In both study groups, levothyroxine decreased thyroid antibody titres, reduced thyrotropin levels and increased free thyroid hormone levels. However, these effects were less pronounced in the men with early-onset male-pattern baldness than in the control men. The degree of reduction in antibody titres and thyrotropin levels correlated with baseline levels of total and calculated bioavailable testosterone, as well with baseline insulin sensitivity and treatment-induced improvement in insulin sensitivity. Concentrations of the remaining variables remained unchanged throughout the study period. CONCLUSIONS: The results of the current study suggest that the benefits of levothyroxine therapy in men with autoimmune hypothyroidism are less pronounced in individuals with early-onset androgenetic alopecia.

Suppression of thyrotropin secretion during roxadustat treatment for renal anemia in a patient undergoing hemodialysis.

BACKGROUND: Inhibition of hypoxia-inducible factor prolyl hydroxylase (HIF-PH) is a novel choice for the treatment of renal anemia, and an oral HIF-PH inhibitor roxadustat was approved for renal anemia. Roxadustat has high affinity to thyroid hormone receptor beta, which may affect thyroid hormone homeostasis. CASE PRESENTATION: We present here a patient undergoing hemodialysis with primary hypothyroidism receiving levothyroxine replacement, who showed decreased free thyroxine (FT4) and thyroid stimulating hormone (TSH) after starting roxadustat. Pituitary stimulation test revealed selective suppression of TSH secretion. Recovery of TSH and FT4 levels after stopping roxadustat suggested the suppression of TSH was reversible. CONCLUSIONS: Physicians should pay special attention to thyroid hormone abnormalities in treatment with roxadustat.

Cognitive dysfunction associated with activation of the mTOR signaling pathway after TSH suppression therapy in rats.

Thyroid stimulating hormone (TSH) suppression therapy after thyroid carcinoma surgery could lead to cognitive impairment. But, the possible mechanism of TSH suppression therapy impairs cognitive function is yet unknown. In this study, forty Wistar rats were randomized into the sham operation control (OC), total thyroidectomy (TD), thyroxine replacement therapy (TR), and TSH suppression therapy (TS) groups. We observed that compared to the OC group, escape latency on 1-4 days was significantly prolonged in the TD and TS groups, and the number of rats crossing the virtual platform was significantly reduced in the TD and TS groups. In the TD, TR, and TS groups, the residence time in the target quadrant was significantly decreased, while the activity distance in the target quadrant in the TD group was significantly decreased compared with OC group. In the TD and TS groups, the pyramidal cells in the hippocampal CA1 region showed a disordered arrangement. The cytoplasm was lightly stained, the cells were swollen and round, and spotty liquefaction necrosis could be observed. Compared to the OC group, hippocampal p-mTOR and p-p70s6k levels were significantly decreased in the TD group, while no significant changes were detected in the TR group. Hippocampal p-mTOR and p-p70s6k amounts in the TS group were significantly increased compared with OC group. These results indicated that TSH suppression therapy after total thyroidectomy in rats could impair cognitive function, which might be related to the activation of the mTOR signaling pathway and the damage and necrosis of hippocampal neurons.

When thyroid labs do not add up, physicians should ask patients about biotin supplements.

A 69-year-old woman with a remote history of Graves' disease treated with radioactive iodine ablation, who was maintained on a stable dose of levothyroxine for 15 years, presented with abnormal and fluctuating thyroid function tests which were confusing. After extensive evaluation, no diagnosis could be made, and it became difficult to optimise the levothyroxine dose, until we became aware of the recently recognised biotin-induced lab interference. It was then noticed that her medication list included biotin 10 mg two times per day. After holding the biotin and repeating the thyroid function tests, the labs made more sense, and the patient was easily made euthyroid with appropriate dose adjustment. We also investigated our own laboratory, and identified the thyroid labs that are performed with biotin-containing assays and developed strategies to increase the awareness about this lab artefact in our clinics.

Investigation of thyroid function in dogs treated with the tyrosine kinase inhibitor toceranib.

Tyrosine kinase inhibitors are widely utilized in veterinary oncology for the treatment of mast cell and solid tumours. In man, these drugs are associated with thyroid dysfunction: however, to date only one study has investigated this in dogs. The aim of this study was to prospectively assess thyroid function in a group of dogs with cancer receiving toceranib. Thirty-four dogs were prospectively enrolled at two referral hospitals into two groups; those receiving toceranib with prednisolone and those receiving toceranib alone. Total thyroxine (TT4) and thyroid stimulating hormone (TSH) was monitored at regular time points during treatment. Follow-up data was available for 19 dogs. Overall, 12 incidences of elevated TSH occurred but none of these dogs had concurrent low TT4 concentrations. There was a significant difference in median TSH at week six compared with baseline. Hypothyroidism was not diagnosed in any patient during the study period. Patient drop-out was higher than anticipated which prevented the assessment of longer term toceranib administration on thyroid function. Toceranib therapy was not associated with hypothyroidism in this study but did result in elevations in TSH which confirms what has been previously reported. Toceranib should be considered to cause thyroid dysfunction in dogs and monitoring is advised.

Cleavage Region Thyrotropin Receptor Antibodies Influence Thyroid Cell Survival In Vivo.

Background: Graves' disease is associated with thyrotropin receptor (TSHR) antibodies of variable bioactivity. Recently, antibodies have been characterized that bind to the cleavage region of the TSHR ectodomain (C-TSHR-Ab), and their ability to induce thyroid cell apoptosis in vitro via excessive cell stress involving multiple organelles was demonstrated. Methods: To investigate the in vivo effects of C-TSHR-Ab, first a murine monoclonal antibody (mAb) directed against residues 337 to 356 of the TSHR cleavage region was developed, and then it was injected into mice. Results: These injections caused reduced serum total triiodothyronine and thyroxine and increased TSH levels compared to control mAb-injected mice. The C-TSHR-mAb induced histological evidence of endoplasmic reticulum stress, mitochondrial stress, and apoptosis in the thyroid glands. C-TSHR-mAb-mediated apoptosis was associated with cellular infiltrates consisting mostly of macrophages, dendritic cells, and neutrophils, while T- and B-lymphocytes were scarce. In addition, in the treated mouse thyroid tissue, hyper-citrullination of histone H3 was also found. This is known to occur via peptidylarginine deiminase 4 and plays an important role in the formation of neutrophil extracellular traps, which are likely to be partly responsible for thyroid infiltration, as seen in many autoimmune diseases. Examination of thyroid tissue from patients with Graves' disease also showed increased stress and some thyrocyte apoptosis compared to normal thyroid tissues. Conclusions: The fact that the C-TSHR-mAb induced accumulation of macrophages, neutrophils, and dendritic cells indicates that innate immunity plays a central role in shaping the adaptive immune response to the TSHR. In addition, this study provides further evidence that the hinge region of the TSHR ectodomain is intimately involved in the immune response in autoimmune thyroid disease.

Thyroid Hormone Suppression Therapy.

Thyroid hormone suppression therapy is designed to lower serum thyrotropin (TSH) levels using doses of thyroid hormone in excess of what would normally be required to maintain a euthyroid state. The basis of this therapy is the knowledge that TSH is a growth factor for thyroid cancer, so that lower serum TSH levels might be associated with decreased disease activity. However, clinical studies have not documented improved outcomes with TSH suppression, except in patients with the most advanced disease. Furthermore, there are a number of negative outcomes related to aggressive thyroid hormone therapy, including osteoporosis, fracture, and cardiovascular disease. Therefore, a graded approach to TSH suppression is recommended by the American Thyroid Association, based on initial risk and ongoing risk assessment.

The Relationship Between Statin Action On Thyroid Autoimmunity And Vitamin D Status: A Pilot Study.

BACKGROUND: Both vitamin D preparations and high-dose statin therapy were found to reduce thyroid antibody titers. OBJECTIVE: The purpose of this study was to assess whether vitamin D status determines the effect of statin therapy on thyroid autoimmunity. METHODS: The study population consisted of 39 euthyroid women with Hashimoto's thyroiditis and moderate or moderately high cardiovascular risk divided into two groups: women with vitamin D deficiency or insufficiency (group A; n=19) and women with normal vitamin D status (group B, n=20). All patients received atorvastatin therapy (20-40 mg daily) for the following 6 months. Plasma lipids, circulating levels of thyrotropin, free thyroid hormones, prolactin and 25-hydroxyvitamin D, titers of thyroid peroxidase and thyroglobulin antibodies, as well as Jostel's, the SPINA-GT and the SPINA-GD indices were assessed at the beginning and at the end of the study. RESULTS: The study completed all women. At baseline, with the exception of 25-hydroxyvitamin D, there were no significant differences between both study groups in plasma lipids, circulating hormone levels and titers of thyroid peroxidase and thyroglobulin antibodies. Despite improving plasma lipids in both study groups, atorvastatin reduced thyroid antibody titers only in women with normal vitamin D status. Moreover, in this group of patients, atorvastatin increased the SPINA-GT index. Circulating levels of the measured hormones, Jostel's thyrotropin index and the SPINA-GD index remained at a similar level throughout the study. CONCLUSIONS: The results of the study suggest that the effect of atorvastatin therapy on thyroid autoimmunity depends on vitamin D status.

Lipid and thyroid hormone levels in children with epilepsy treated with levetiracetam or carbamazepine: A prospective observational study.

Although previous studies have investigated the influence of antiepileptic drugs (AEDs) on lipid profiles and thyroid hormone levels, there is little evidence regarding the effects of levetiracetam (LEV). Therefore, we conducted a prospective longitudinal study to evaluate the effects of LEV and carbamazepine (CBZ) treatment on lipid profile and thyroid hormone levels in patients newly diagnosed with epilepsy. Inclusion criteria were as follows: (a) age between 4 and 15 years, (b) diagnosis of epilepsy with at least two focal seizures within a year, and (c) newly treated with LEV or CBZ monotherapy. Serum lipid profile and thyroid hormone levels were measured before and after 1 and 6 months of AED initiation. Among the 21 included patients (LEV: 13 patients, CBZ: 8 patients), all but one patient in the LEV group continued AED monotherapy during the study period. Although triglyceride (TG) levels tended to be increased in the CBZ group (baseline: 58.3 ±â€¯22.0 mg/dl, 1 month: 63.8 ±â€¯21.6 mg/dl, 6 months: 92.3 ±â€¯63.6 mg/dl, p = 0.22, analyses of variance (ANOVA)), there were no significant changes in total cholesterol (TC), TG levels, high-density lipoprotein cholesterol (HDL-C), or low-density lipoprotein cholesterol (LDL-C) in either group. Serum free thyroxine (fT4) levels were significantly decreased in the CBZ group (baseline: 1.15 ±â€¯0.06 ng/dl, 1 month: 1.00 ±â€¯0.16 ng/dl, 6 months: 0.98 ±â€¯0.14 ng/dl, p = 0.03, ANOVA). In contrast, there were no significant changes in fT4 or thyroid-stimulating hormone (TSH) levels in the LEV group. The results of the present study suggest that LEV monotherapy does not affect lipid profile or thyroid function while CBZ monotherapy may cause thyroid dysfunction.

Myo-inositol in autoimmune thyroiditis, and hypothyroidism.

Myo-inositol (Myo-Ins) plays an important role in thyroid function and autoimmunity. Myo-Ins is the precursor for the synthesis of phosphoinositides, which takes part in the phosphatidylinositol (PtdIns) signal transduction pathway, and plays a decisive role in several cellular processes. In the thyroid cells, PtdIns is involved in the intracellular thyroid-stimulating hormone (TSH) signaling, via Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) (PIP-3). Moreover, the phosphatidyl inositol 3 kinases (PI3K) family of lipid kinases regulates diverse aspects of T, B, and Tregs lymphocyte behaviour. Different mouse models deficient for the molecules involved in the PIP3 pathway suggest that impairment of PIP3 signaling leads to dysregulation of immune responses and, sometimes, autoimmunity. Studies have shown that cytokines modulate Myo-Ins in thyroid cells. Moreover, clinical studies have shown that after treatment with Myo-inositol plus seleniomethionine (Myo-Ins + Se), TSH levels significantly declined in patients with subclinical hypothyroidism due to autoimmune thyroiditis. The treatment was accompanied by a decline of antithyroid autoantibodies. After treatment serum CXCL10 levels declined, confirming the immune-modulatory effect of Myo-Ins. Additional research is necessary in larger population to evaluate the effect on the quality of life, and to study the mechanism of the effect on chemokines.

Free thyroxine and thyroid-stimulating hormone in severe mental disorders: A naturalistic study with focus on antipsychotic medication.

BACKGROUND: Disturbances in thyroid function have been associated with use of psychotropic drugs, including antipsychotics. Still, the thyroid function in relation to commonly prescribed antipsychotic drugs and polypharmacy is not fully known. We investigated thyroid function associated with use of antipsychotics in patients with psychotic disorders compared with healthy controls. METHODS: We included 1345 patients and 989 healthy controls from the Thematically Organized Psychosis (TOP) study, recruiting participants between 18 and 65 years of age in the Oslo-area. All patients underwent a thorough clinical investigation and assessment of medication data. Thyroid function was determined from plasma levels of free thyroxin (fT4) and thyroid-stimulating hormone (TSH). Multiple linear regression analyses were performed to evaluate the association between thyroid parameters and use of antipsychotics, and monotherapy users of olanzapine, quetiapine, aripiprazole or risperidone (N = 473) were investigated separately. RESULTS: We found lower levels of fT4 (median 13.70 vs 14.00, p < 0.001) in patients compared to healthy controls, and a prevalence of 12.9% of previously undiagnosed deviant thyroid states in the patient group. Lower fT4 levels was associated with use of antipsychotics in general (p = 0.001), and quetiapine (p = 0.003) and olanzapine (p = 0.018) in particular, while the associations with TSH were non-significant. Using antipsychotics in combination with other psychotropic drugs, and with antidepressants in particular, was associated with lower fT4 level (p < 0.001) than use of antipsychotics alone. CONCLUSIONS: Our findings indicate an association between use of antipsychotics and lower fT4. Clinicians should be aware that patients using quetiapine, olanzapine or antipsychotics in psychotropic polypharmacy are especially at risk.

Possible protective effect of curcumin on the thyroid gland changes induced by sodium fluoride in albino rats: light and electron microscopic study.

OBJECTIVES: Thyroid gland regulates the body's metabolic rate and plays an exquisitely important role in the human health. Fluoride exposure can affect thyroid function. Curcumin is a potent antioxidant that works through several mechanisms. The aim of the present study was to demonstrate the hormonal, histological, and ultrastructural changes occurred in the thyroid gland induced by exposure to sodium fluoride (NaF) and study the possible protective effect of curcumin on the NaF-induced effects. METHODS: Thirty male albino rats were randomly divided into 3 equal groups (10 rats each): the control group, NaF group, and NaF+Curcumin (NaF+Cur) group. Thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) levels were assayed and thyroid tissues processed for light and transmission electron microscopic study. RESULTS: In NaF group, serum T3 and T4 levels were significantly decreased whereas TSH level was significantly increased compared to the control group. Thyroid tissues showed flattening of the epithelial lining with several follicular cell degenerations, hyperplasia, decreased colloid, disrupted basement membrane, cytoplasmic vacuolations, degenerated mitochondria, widening of rough endoplasmic reticulum cisternae, and vascular congestion compared to the control group. In the NaF+Cur group, serum TSH levels were significantly decreased in comparison with NaF group and no significant difference in comparison with the control group. Thyroid sections appeared apparently normal compared to the control group and NaF group. CONCLUSIONS: Sodium fluoride affected both the function and structure of the thyroid gland while curcumin was protective against these toxic effects.

Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case- Control Study.

The elevated fluoride from drinking water impacts on T3, T4 and TSH hormones. The aim was study impacts of drinking water fluoride on T3, T4 and TSH hormones inYGA (Yazd Greater Area). In this case- control study 198 cases and 213 controls were selected. Fluoride was determined by the SPADNS Colorimetric Method. T3, T4 and TSH hormones tested in the Yazd central laboratory by RIA (Radio Immuno Assay) method. The average amount of TSH and T3 hormones based on the levels of fluoride in two concentration levels 0-0.29 and 0.3-0.5 (mg/L) was statistically significant (P = 0.001 for controls and P = 0.001 for cases). In multivariate regression logistic analysis, independent variable associated with Hypothyroidism were: gender (odds ratio: 2.5, CI 95%: 1.6-3.9), family history of thyroid disease (odds ratio: 2.7, CI 95%: 1.6-4.6), exercise (odds ratio: 5.34, CI 95%: 3.2-9), Diabetes (odds ratio: 3.7, CI 95%: 1.7-8), Hypertension (odds ratio: 3.2, CI 95%: 1.3-8.2), water consumption (odds ratio: 4, CI 95%: 1.2-14). It was found that fluoride has impacts on TSH, T3 hormones even in the standard concentration of less than 0.5 mg/L. Application of standard household water purification devices was recommended for hypothyroidism.

Reduced insulin sensitivity in differentiated thyroid cancer patients with suppressed TSH.

OBJECTIVE: TSH-suppression is a therapy for thyroid cancer management, but it may lead to adverse effects, which should be balanced with its benefits. Previous studies evaluating the consequences of TSH suppression on insulin sensitivity have only been done with indirect techniques, and results were controversial. Therefore, we aimed to assess insulin sensitivity in patients with thyroid cancer and suppressed thyroid-stimulating hormone (TSH) with the most appropriate direct method (hyperinsulinemic-euglycemic clamp) in order to get a more conclusive response about the topic. METHODS: A group of 20 non-obese and non-diabetic thyroid cancer patients with suppressed TSH underwent a hyperinsulinemic-euglycemic clamp to evaluate insulin sensitivity. Their results were compared to the results of a sex and body mass index (BMI) -paired control group composed of 20 healthy volunteers. RESULTS: Patients were all female, aged 36.8 ± 10.2 years-old, with mean TSH 0.1 ± 0.1 µIU/mL and mean BMI 26.2 ± 3.3 kg/m2. Insulin sensitivity, determined by the insulin-stimulated glucose uptake (M-value), was lower in the patients group (4.2 ± 1.6 mg/min*kg versus 5.8 ± 1.7, age-adjusted p-value = 0.0205). CONCLUSION: This study shows for the first time that subclinical thyrotoxicosis in patients with thyroid cancer is associated with insulin resistance, as measured by hyperinsulinemic-euglycemic clamp technique. Such finding may be taken into consideration by clinicians when balancing risks and benefits of TSH-suppression therapy in thyroid cancer patients.

Thyroid-stimulating hormone suppression therapy for differentiated thyroid cancer: The role for a combined T3/T4 approach.

BACKGROUND: In the management of differentiated thyroid carcinoma, surgery with or without postoperative radioiodine, and thyroid-stimulating hormone (TSH) suppression is the standard of care in most patients. Levothyroxine is recommended for long-term TSH suppression. For some patients, this may be difficult to tolerate due to adverse effects, such as impaired cognitive function. METHODS: This article reviews the evidence for the role of combination treatment with triiodothyronine (T3) and levothyroxine (T4) in these patients. RESULTS: The evidence for combination T3 and T4 treatment comes mainly from studies on hypothyroidism, and research into its use for TSH suppression is limited. CONCLUSION: Although the evidence base is not strong, there is a small group of patients who may benefit from combination T3 and T4 treatment due to difficulty tolerating thyroxine. Until further evidence is available, a case-by-case approach is recommended.

Clinical and immunological changes in patients with active moderate-to-severe Graves' orbitopathy treated with very low-dose rituximab.

INTRODUCTION: Glucocorticoids represent the therapy of choice for active and moderate-to-severe Graves' orbitopathy (GO). In some patients, rituximab, a monoclonal antibody against the cluster of differentiation (CD) 20 receptor of B-lymphocytes, can serve as a second-line or an alternative treatment. The effect of very low-dose of rituximab on the clinical activity of GO and corresponding clinical or laboratory changes is reported. MATERIAL AND METHODS: Changes of Clinical Activity Score (CAS) for GO, proptosis, levels of thyroid-stimulating hormone receptor antibodies, and depletion of CD19+ and CD20+ B-lymphocytes were determined in ten patients (two men and eight women) with active moderate-to-severe GO treated with a single 100-mg dose of rituximab. Correlations between differences of clinical and laboratory parameters were performed. RESULTS: A significant decrease of CAS was found during subsequent examinations compared to the baseline values. A significant depletion of CD19+ and CD20+ B-lymphocytes was detected after rituximab administration. Differences between follow-up and baseline levels of CD20+ positively correlated with differences in CAS after six (p < 0.05) and 12 months (p < 0.01). Differences in CD19+ levels correlated with differences in CAS after 12 months (p < 0.05) of the treatment. Two patients developed dysthyroid optic neuropathy (DON) requiring orbital decompression. No other rituximab side effects were reported during the whole study duration. CONCLUSIONS: A single very low-dose of rituximab appears to be very well tolerated and effective enough to reduce clinical activity in active moderate-to-severe GO patients without impending DON.

Delayed TSH recovery after dose adjustment during TSH-suppressive levothyroxine therapy of thyroid cancer.

BACKGROUND: Delayed thyroid-stimulating hormone (TSH) recovery during treatment of Graves' disease is caused by long-term excessive thyroid hormone, which results in downregulation of pituitary thyrotrophs. However, it is unknown whether delayed TSH recovery exists after levothyroxine (LT4) dose reduction in patients with differentiated thyroid cancer (DTC) after long-term TSH suppression. METHODS: We retrospectively reviewed 97 DTC patients with LT4 dose reduction after long-term TSH suppression. TSH levels at baseline (point 1), 6 months (point 2) and 12-18 months (point 3) after LT4 dose reduction were compared. A delayed TSH recovery group whose TSH levels changed to upper target TSH category (2015 revised ATA guidelines) from point 2 to point 3 was identified, and risk factors were analysed. RESULTS: The median TSH level at point 3 was significantly higher than that of point 2 (0.17 vs 0.09 mIU/L; P<.001). The delayed TSH recovery group (44.3%) showed increased body weight (60.84 vs 62.73 kg; P=.01), while normal response group did not. Greater reduction (%) in the LT4 dose per weight [HR 1.10, 95% CI (1.00-1.22), P=.04] and higher BMI before thyroid surgery [1.19, 1.03-1.38, P=.01] predicted the occurrence of delayed TSH recovery, while higher dose of LT4 per weight after reduction showed preventive effect [HR 0.01, 95% CI (0.00-0.54); P=.02]. CONCLUSIONS: Delayed TSH recovery was common during LT4 dose reduction after long-term TSH suppression for DTC management. Six months may not be enough for TSH recovery and to evaluate thyroid hormone status by serum TSH.