Factors influencing TSH suppression efficacy in postoperative papillary thyroid carcinoma patients: a retrospective cohort study.

OBJECTIVES: While surgery plays a crucial role in treating papillary thyroid carcinoma (PTC), the potential effects of subsequent TSH suppression therapy on prognosis should not be overlooked. This study aims to investigate the factors that influence postoperative TSH suppression therapy in patients with PTC. METHODS: This study was a retrospective cohort study conducted at our hospital. It included 268 patients who underwent surgery and were pathologically diagnosed with PTC between February 2019 and February 2021. The selected patients received postoperative TSH suppression therapy. Based on the TSH level measured 12 months after surgery, the patients were divided into two groups: TSH level conforming group (n = 80) and non-conforming group (n = 188). We then compared the general clinical data, clinicopathological characteristics, preoperative laboratory test indicators, postoperative levothyroxine sodium tablet dosage, follow-up frequency, and thyroid function-related indicators between the two groups of patients. The correlation between the observed indicators and the success of TSH suppression therapy was further analyzed, leading to the identification of influencing factors for TSH suppression therapy. RESULTS: There were no statistically significant differences in general clinical data and clinicopathological characteristics between the two groups of patients (P > 0.05). The proportion of patients with preoperative TSH ≥ 2.0 mU/L was higher in the non-conforming group compared to the TSH level conforming group (P < 0.05), and the ROC curve analysis indicated that the area under the curve for the preoperative TSH index was 0.610 (P < 0.05). The proportion of patients in the TSH level conforming group who took oral levothyroxine sodium tablets at a dose of ≥ 1.4 µg/kg·d after surgery was higher (P < 0.05). The postoperative levels of FT3 and FT4 were higher in the TSH level conforming group (P < 0.05). The results of binary logistic regression analysis indicated that factors "Postoperative TSH level ≥ 2 mU/L", "Levothyroxine sodium tablet dose<1.4 µg/kg·d", and "Combined with Hashimoto thyroiditis" were significantly associated with an elevated risk of postoperative TSH levels failing to reach the target (P < 0.05). CONCLUSION: Optimal thyroid function in patients with PTC post-surgery is best achieved when adjusting the dose of levothyroxine sodium in a timely manner to reach the target TSH level during follow-up visits.

Growth impairment in children with atrophic autoimmune thyroiditis and pituitary hyperplasia.

BACKGROUND: Atrophic autoimmune thyroiditis (AAT) is a rare phenotype of autoimmune thyroiditis (AT) in pediatric age. AAT occurs without thyroid enlargement leading to a delay in its diagnosis. Growth impairment is infrequent in autoimmune thyroiditis, if timely diagnosed. Prolonged severe hypothyroidism is a rare cause of pituitary hyperplasia (PH) in childhood. Loss of thyroxine negative feedback causes a TRH-dependent hyperplasia of pituitary thyrotroph cells resulting in adenohypophysis enlargement. A transdifferentiation of pituitary somatotroph cells into thyrotroph cells could explain growth failure in those patients. METHODS: Twelve patients were retrospectively evaluated at five Italian and Polish Centres of Pediatric Endocrinology for height growth impairment. In all Centres, patients underwent routine clinical, biochemical and radiological evaluations. RESULTS: At the time of first assessment, the 75% of patients presented height growth arrest, while the remaining ones showed growth impairment. The study of thyroid function documented a condition of hypothyroidism, due to AT, in the entire cohort, although all patients had no thyroid enlargement. Thyroid ultrasound showed frankly atrophic or normal gland without goiter. Cerebral MRI documented symmetrical enlargement of the adenohypophysis in all patients and a homogeneous enhancement of the gland after the administration of Gadolinium-DPTA. Replacement therapy with levothyroxine was started and patients underwent close follow-up every 3 months. During the 12 months of follow-up, an improvement in terms of height growth has been observed in 88% of patients who continued the follow-up. Laboratory findings showed normalization of thyroid function and the control brain MRI documented complete regression of PH to a volume within the normal range for age and sex. CONCLUSIONS: This is the largest pediatric cohort with severe autoimmune primary hypothyroidism without goiter, but with pituitary hyperplasia in which significant growth impairment was the most evident presenting sign. AAT phenotype might be correlated with this specific clinical presentation. In youths with growth impairment, hypothyroidism should always be excluded even in the absence of clear clinical signs of dysthyroidism.

Aversion of surgical exploration in patients with complex ovarian cysts secondary to overt hypothyroidism: A series of three cases.

Long-standing, overt hypothyroidism-induced bilateral multiloculated ovarian cysts represent an infrequent occurrence. Our first case, presented with bilateral complex ovarian masses, exhibited overt hypothyroidism symptoms, including lethargy, weight gain and subfertility, prompting consideration for surgical intervention. Similarly, in the second case, a girl aged 11 years with stunting, delayed bone age and academic challenges was referred for surgical exploration due to bilateral complex ovarian masses. Both cases revealed elevated thyroid-stimulating hormone levels during preoperative workup. Commencing levothyroxine replacement therapy resulted in complete regression of ovarian cysts and substantial symptom improvement within an 8-week timeframe. The third case, a previously diagnosed patient with Hashimoto's thyroiditis, benefited from the lessons gleaned in managing the initial cases, responding well to levothyroxine therapy, thereby averting the necessity for surgery in all three instances. These cases underscore the significance of considering thyroid function in the evaluation of ovarian masses and highlight the efficacy of levothyroxine replacement therapy in resolving both hypothyroidism and associated ovarian cysts, thereby obviating the need for surgical intervention.

Risk of Subsequent Primary Cancers in Thyroid Cancer Survivors according to the Dose of Levothyroxine: A Nationwide Cohort Study.

BACKGRUOUND: Current research has not investigated the effect of thyroid-stimulating hormone suppression therapy with levothyroxine on the risk for developing subsequent primary cancers (SPCs). This study aimed to investigate the association between levothyroxine dosage and the risk for SPCs in thyroid cancer patients. METHODS: We conducted a nationwide population-based retrospective cohort study form Korean National Health Insurance database. This cohort included 342,920 thyroid cancer patients between 2004 and 2018. Patients were divided into the non-levothyroxine and the levothyroxine groups, the latter consisting of four dosage subgroups according to quartiles. Cox proportional hazard models were performed to evaluate the risk for SPCs by adjusting for variables including cumulative doses of radioactive iodine (RAI) therapy. RESULTS: A total of 17,410 SPC cases were observed over a median 7.3 years of follow-up. The high-dose levothyroxine subgroups (Q3 and Q4) had a higher risk for SPC (adjusted hazard ratio [HR], 1.14 and 1.27; 95% confidence interval [CI], 1.05-1.24 and 1.17- 1.37; respectively) compared to the non-levothyroxine group. In particular, the adjusted HR of stomach (1.31), colorectal (1.60), liver and biliary tract (1.95), and pancreatic (2.48) cancers were increased in the Q4 subgroup. We consistently observed a positive association between high levothyroxine dosage per body weight and risk of SPCs, even after adjusting for various confounding variables. Moreover, similar results were identified in the stratified analyses according to thyroidectomy type and RAI therapy, as well as in a subgroup analysis of patients with good adherence. CONCLUSION: High-dose levothyroxine use was associated with increased risk of SPCs among thyroid cancer patients regardless of RAI therapy.

Development of hypothyroidism following hemithyroidectomy: A population-based study.

PURPOSE: Hypothyroidism is a known possibility after hemithyroidectomy, with a highly variable incidence in the literature ranging from 8 to 60 %. Incidence of hypothyroidism after hemithyroidectomy was evaluated with a secondary aim to assess incidence in patients with Hashimoto's disease. MATERIALS & METHODS: A retrospective study using the TriNetX global federated research network was performed. We included patients within the last 15 years that were ≥18 years of age and had Current Procedural Terminology codes for hemithyroidectomy. Patients were excluded if they had a total or completion thyroidectomy at any time, a history of thyroid cancer, were preoperatively either on levothyroxine, diagnosed with hypothyroidism, or had a Thyroid Stimulating Hormone ≥ 4 m[IU]/L. We assessed the 3 month incidence of hypothyroidism postoperatively based on the International Classification of Diseases code, TSH ≥ 4 m[IU]/L, or taking levothyroxine after surgery. RESULTS: 6845 patients met the inclusion criteria. Most of the cohort was female (67 %) and white (63 %). The mean age at surgery for this population was 54 ± 14.8 years. During the 15 years of data, we found the 3-month incidence of hypothyroidism following hemithyroidectomy to be 23.58 %. The median time to develop the disease was 41.8 months. A subgroup analysis of those with Hashimoto's revealed a 3-month incidence of 31.1 % of patients developing hypothyroidism after surgery. CONCLUSIONS: This population-based study gives additional insight into the incidence of hypothyroidism after hemithyroidectomy. This will help improve perioperative patient counseling and management.

Ectopic lingual thyroid with subclinical hypothyroidism in children.

OBJECTIVES: Lingual thyroid is a rare condition that affects approximately 1 in 100,000 individuals. Although it is usually detected in the pediatric population through newborn screening tests or evaluation of congenital hypothyroidism, there are cases in which it remains undetected until adulthood or until symptoms arise because of glandular enlargement. The possible symptoms of lingual thyroid include foreign body sensation in the throat, dysphagia, dyspnea, and hemorrhage. Several cases of lingual thyroid are asymptomatic and accompanied by subclinical hypothyroidism. Herein, we present three cases of lingual thyroid treated with thyroid hormone suppressive therapy. CASE PRESENTATION: The three patients sought medical attention because of a sore throat or foreign body sensation in the throat. Their newborn screening tests and developmental histories were normal. These patients exhibited subclinical hypothyroidism and were treated with hormone suppression therapy. CONCLUSIONS: Patients with lingual thyroid frequently exhibit subclinical hypothyroidism. Hormone treatment may help to reduce the size of the ectopic thyroid and improve symptoms. If an increase in size is noted during follow-up or symptoms do not improve, surgical treatments may be considered.

Analysis of dose-TSH response effect of levothyroxine soft-gel formulation.

Background: Hypothyroidism is treated with daily levothyroxine (LT4). In recent years, soft gel caps of LT4 (LT4-C) have been commercialized, and their performance has been optimized. Since guidelines recommend dose LT4 according to the tablet preparation efficacy, the present study was undertaken to obtain data about the daily requirement, normalized per body weight, of LT4-C. Methods: Patients undergoing LT4-C after total thyroidectomy and radioiodine treatment for differentiated thyroid carcinoma were selected. There was no specific indication of suppression of TSH (i.e., <0.5 or <0.1 mIU/L). Patients were required to maintain a stable LT4 dose during the study period. Patients with interfering factors were excluded from this study. Results: Thirty patients were enrolled (18 females and 12 males; median age, 50 years; median body weight, 71 kg; median LT4-C dose, 1.71 µg/kg/day). The analysis of patient age did not reveal any differences. The LT4-C dose correlated with free-T4 p = 0.03), but not with TSH (p = 0.42) and free-T3 (p = 0.13). TSH was <1.0 mIU/L in 90% of the cases. The LT4-C dose-TSH response effect was analysed by probit regression model: the probability to achieve TSH <1.0 mIU/l was 99% with a dose of 1.84 (95%CI 1.57-2.12) µg/kg/day, 75% with a dose of 1.38 µg/kg/day (95%CI 1.17-1.59), and 50% with a dose of 1.20 (95%CI 0.96-1.43). At ROC curve analysis, the most accurate cut-off of LT4-C dose to achieve TSH <1.0 mIU/l was 1.53 ug/kg/day with 70% sensitivity and 100% specificity. Conclusions: Athyreotic patients can be initially treated with an LT4-C dose lower than previously stated. Therefore, further prospective studies are warranted.

Comparison of pathophysiology in subclinical hyperthyroidism with different etiologies.

Subclinical hyperthyroidism (SHyper) is defined as normal levels of free thyroxine (fT4) and free triiodothyronine (fT3) with suppressed levels of TSH. Previous studies have reported the individual pathophysiology of endogenous SHyper patients and athyreotic patients receiving TSH suppression therapy with levothyroxine; however, apparently no studies have compared the two conditions. Five-hundred-forty untreated endogenous SHyper patients and 1,024 patients receiving TSH suppression therapy who underwent total thyroidectomy for papillary thyroid carcinoma were sampled. Thyroid hormone profiles and peripheral indices related to thyrotoxicosis were investigated in endogenous SHyper patients, athyreotic patients receiving TSH suppression therapy, and healthy participants. Endogenous SHyper patients showed significantly higher thyroid hormone levels (fT4 [p < 0.001] and fT3 [p < 0.001]), and peripheral indices showed a significant tendency towards thyrotoxicosis (strong TSH suppression: alkaline phosphatase [ALP, p < 0.001], creatinine [Cre, p < 0.001], pulse rate [p < 0.05]; and mild TSH suppression: Cre [p < 0.05]) than healthy participants. In contrast, athyreotic patients receiving TSH suppression therapy showed a significant tendency towards thyrotoxicosis than healthy participants only when TSH was strongly suppressed (fT3 [p < 0.001] and Cre [p < 0.001]). Endogenous SHyper patients showed significantly higher fT3 levels (p < 0.001) than athyreotic patients receiving TSH suppression therapy; however, there was a significant tendency towards thyrotoxicosis only when TSH was strongly suppressed (ALP [p < 0.05] and pulse rate [p < 0.05]). The effects of endogenous SHyper and TSH suppression therapy on target organ function are different. Although the serum thyroid hormone profile is similar to that of the thyrotoxic state, athyreotic patients receiving TSH suppression therapy with mildly suppressed serum TSH levels are not thyrotoxic.

Levothyroxine and Non-alcoholic Fatty Liver Disease: A Mini Review.

Levothyroxine or l-thyroxine is artificially manufactured thyroxine, which is used as a drug to treat underactive thyroid conditions in humans. The drug, levothyroxine, is consumed daily in a prescribed dose to replace the missing thyroid hormone thyroxine in an individual with an underactive thyroid, and it helps to maintain normal physiological conditions. Though it is a life-maintaining drug, it replaces the missing thyroid hormone and performs the necessary daily metabolic functions in our body. Like all other allopathic drugs, it comes with certain side effects, which include joint pain, cramps in muscle, weight gain/loss, hair loss, etc. The thyroid hormone, thyroxine, is known to mobilize fat in our body, including the ones from the hepatic system. An underactive thyroid may cause an accumulation of fat in the liver, leading to a fatty liver, which is clinically termed Non-Alcoholic Fatty Liver Disease (NAFLD). The correlation between hypothyroidism and NAFLD is now well-studied and recognized. As levothyroxine performs the functions of the missing thyroxine, it is anticipated, based on certain preliminary studies, that the drug helps to mobilize hepatic fat and thus may have a crucial role in mitigating the condition of NAFDL.

Insight of the Biopharmaceutical Implication of Sleeve Gastrectomy on Levothyroxine Absorption in Hypothyroidism Patients.

PURPOSE: The growing rate of obesity led to an increased number of bariatric surgeries (BS) as a treatment option for obesity. The gastrointestinal tract (GIT) changes following BS can impact many drugs' absorption. Levothyroxine (LT4) is a synthetic thyroxine (T4) replacement used commonly as tablets to manage hypothyroidism disorder, which is more prevalent among patients with obesity. This study aims to examine the LT4 oral tablet form therapy after sleeve gastrectomy. MATERIALS AND METHODS: A retrospective cohort study was conducted in multi-center. The LT4 doses and TSH and T4 levels were compared before and after BS. The post-surgery readings were categorized into three periods: (one to three months), (four to six months), and (> six ) months after surgery. ANOVA test was used for analysis. RESULTS: A total of 14374 patients who underwent BS from (1/2019 to 3/2022) were screened for eligibility, and n = 101 participants matched the inclusion criteria. The TSH and T4 were not statistically significant differences before and after surgery (P-values of 0.4864 and 0.5970, respectively). However, the doses significantly differed before and after surgery in all the follow-up time point periods (P < 0.002). CONCLUSION: The LT4 required doses significantly reduced after sleeve gastrectomy, which can be related to the improved endogenous thyroid production in patients with obesity. However, the abnormality of the GIT induced by the sleeve gastrectomy may affect the exogenous LT4 absorption. Using liquid forms of LT4 while monitoring the thyroid function parameters can optimize the treatment after the procedure.

Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals.

Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.

Levothyroxine for a high-normal TSH in unexplained infertility.

OBJECTIVE: Unexplained infertility affects nearly one-third of infertile couples. Women with unexplained infertility are more likely to have a high-normal thyroid-stimulating hormone level (TSH: 2.5-5 mIU/L) compared to women with severe male factor infertility. Practice guidelines vary on whether treatment should be initiated for TSH levels >2.5 mIU/L in women attempting conception because the effects of treating a high-normal TSH level with levothyroxine are not known. We evaluated conception and live birth rates in women with unexplained infertility and high-normal TSH levels. DESIGN, PATIENTS AND MEASUREMENTS: Retrospective study including 96 women evaluated for unexplained infertility at a large academic medical centre between 1 January 2000 and 30 June 2017 with high-normal TSH (TSH: 2.5-5 mIU/L and within the normal range of the assay) who were prescribed (n = 31) or not prescribed (n = 65) levothyroxine. Conception and live birth rates were assessed. RESULTS: The conception rate in the levothyroxine group was 100% compared to 90% in the untreated group (p = .086 unadjusted; p < .05 adjusted for age; p = .370 adjusted for TSH; p = .287 adjusted for age and TSH). The live birth rate was lower in the levothyroxine group (63%) compared to the untreated group (84%) (p = .05 unadjusted; p = .094 adjusted for age; p = .035 adjusted for TSH; p = .057 adjusted for age and TSH). CONCLUSIONS: Women with unexplained infertility and high-normal TSH levels treated with levothyroxine had a higher rate of conception but lower live birth rate compared to untreated women, with the limitation of a small sample size. These findings assert the need for prospective, randomized studies to determine whether treatment with levothyroxine in women with unexplained infertility and high-normal TSH is beneficial.

Adequacy of thyroid hormone replacement for people with hypothyroidism in real-world settings: A systematic review and meta-analysis of observational studies.

OBJECTIVE: Thyroid hormone under-replacement and over-replacement are associated with adverse health outcomes. This systematic review aimed to evaluate the extent of thyroid hormone replacement adequacy for patients with known hypothyroidism in real-word settings, excluding those receiving thyroid hormone suppressive therapy as thyroid cancer treatment. DESIGN: Four electronic databases (Embase [Ovid], Medline [Ovid], PubMed and SCOPUS) were searched for published and unpublished observational studies until 12 December 2022. The results of the studies were meta-analysed to calculate pooled prevalence estimates for thyroid hormone supplementation adequacy, over-replacement and under-replacement. Quality assessment of studies was performed using the Joanna-Briggs appraisal tool for prevalence studies. RESULTS: Seven studies with a total of 4230 patients were eligible for quantitative synthesis. The pooled prevalence estimates of adequate thyroid replacement, over-replacement and under-replacement were 0.55 (95% confidence interval [CI]: 0.49-0.60, p = .001), 0.20 (95% CI: 0.14-0.27, p = .001) and 0.24 (95% CI: 0.13-0.36, p = .001), respectively. Four studies subclassified hypothyroidism and hyperthyroidism into overt and subclinical. The pooled prevalence of overt and subclinical hyperthyroidism was 0.04 (95% CI: 0.00-0.11, p = .01) and 0.17 (95% CI: 0.09-0.27 p = .001), respectively. For overt and subclinical hypothyroidism, the pooled prevalence was 0.02 (95% CI: 0.01-0.03, p = .001) and 0.20 (95% CI: 0.12-0.29, p = .001), respectively. CONCLUSIONS: On average, approximately half of patients with hypothyroidism are only treated to target euthyroidism. In real-world practice, a significant number of patients are over-treated or under-treated, leading to adverse healthcare outcomes. It is imperative that more effective thyroid monitoring strategies be implemented, with an emphasis on primary care thyroid function monitoring, to minimise inappropriate thyroid replacement treatments and optimise healthcare outcomes at a population level.

Effect of Thyroid-Stimulating Hormone Suppression Therapy on Cardiac Structure and Function in Patients With Differentiated Thyroid Cancer After Thyroidectomy: A Systematic Review and Meta-Analysis.

OBJECTIVE: We aimed to evaluate the effects of thyroid-stimulating hormone (TSH) suppression therapy on cardiac structure and function in patients with differentiated thyroid cancer (DTC) following thyroidectomy. METHODS: Two investigators independently searched the PubMed, Embase, Cochrane Library, and Web of Science databases for relevant studies published from inception to January 6, 2023, without any restrictions on language. Standard mean differences and 95% confidence intervals were calculated using fixed or random effects models. Thirteen clinical outcomes were analyzed, mainly evaluating cardiac morphology, systolic function, and diastolic function. RESULTS: Thirteen studies were included in the quantitative analysis. Compared to healthy controls, left ventricular mass index, left ventricular posterior wall thickness, interventricular septal thickness, and isovolumic relaxation time values increased; the ratio of E-wave velocity to A-wave velocity and E-wave velocity values decreased. The left ventricular ejection fraction and cardiac output did not change in patients with DTC who underwent long-term TSH suppression therapy. Interventricular septal thickness values were significantly correlated with the duration of TSH suppression therapy. CONCLUSION: Long-term TSH suppression therapy leads to cardiac hypertrophy and impaired cardiac diastolic function in patients with DTC. These changes may be related to the duration of TSH suppression therapy. Large prospective studies with long follow-up periods are needed to validate these findings.

Differentiated thyroid cancer: a focus on post-operative thyroid hormone replacement and thyrotropin suppression therapy.

PURPOSE: This review focuses on post-operative thyroid hormone replacement and thyrotropin suppression therapy in patients with differentiated thyroid cancer. METHODS: A clinical review. RESULTS: Differentiated thyroid cancers (DTC), including papillary and follicular thyroid cancers, have an excellent prognosis and their management leverages a unique set of clinical tools arising from homology to the normal thyroid follicular cell. Surgery is the cornerstone of initial management, and post-operative care often requires thyroid hormone replacement therapy, which may be approached with the intent of physiologic normalization or used pharmacologically to suppress TSH as part of a DTC treatment. CONCLUSION: Management of DTC and approaches to TSH suppression are tailored to an individual's risk of DTC recurrence and are adjusted to a patient's clinical status and comorbidities over time with the goal of mitigating risk and maximizing benefit.

Approach to the Patient With Raised Thyroid Hormones and Nonsuppressed TSH.

Measurement of free thyroid hormones (THs) and thyrotropin (TSH) using automated immunoassays is central to the diagnosis of thyroid dysfunction. Using illustrative cases, we describe a diagnostic approach to discordant thyroid function tests, focusing on entities causing elevated free thyroxine and/or free triiodothyronine measurements with nonsuppressed TSH levels. Different types of analytical interference (eg, abnormal thyroid hormone binding proteins, antibodies to iodothyronines or TSH, heterophile antibodies, biotin) or disorders (eg, resistance to thyroid hormone ß or α, monocarboxylate transporter 8 or selenoprotein deficiency, TSH-secreting pituitary tumor) that can cause this biochemical pattern will be considered. We show that a structured approach, combining clinical assessment with additional laboratory investigations to exclude assay artifact, followed by genetic testing or specialized imaging, can establish a correct diagnosis, potentially preventing unnecessary investigation or inappropriate therapy.

Transition from Hashimoto thyroiditis to Graves's Disease: an unpredictable change?

PURPOSE: Hashimoto thyroiditis and Graves's disease are two related autoimmune disorders, representing the leading causes of hypothyroidism and hyperthyroidism. Autoimmune hypothyroidism is generally irreversible but very rarely, some patients would shift to hyperthyroidism. The aim of the study was to seek for possible clinical predictors of the transition from hypo to hyperthyroidism in patients with Hashimoto thyroiditis and to outline their clinical phenotype. METHODS: Twelve patients with overt autoimmune hypothyroidism who had at least one transition from hypothyroidism to autoimmune hyperthyroidism were compared with 294 consecutive patients with autoimmune hypothyroidism and 69 consecutive patients with autoimmune hyperthyroidism that accessed the outpatient clinic over six months. Demographic, hormonal data and autoantibodies titers were compared. RESULTS: Prevalence of smoking habit was significantly higher in switchers compared to controls. Switchers showed a significantly higher prevalence of personal and familial history of non-thyroidal autoimmune disorders. TSH levels were significantly lower in the switcher group during the hypothyroid phase and levothyroxine dose required was lower. TSH concentrations were significantly lower while free fT4 and free fT3 values were higher in GD patients compared to switchers during the hyperthyroid phase despite comparable TRAb levels. Prevalence and type of hyperthyroid symptoms and orbitopathy were similar between switchers and GD group. Mean dose of anti-thyroid drugs was significantly higher in GD patients compared to switchers. No differences were observed in the remission rate from hyperthyroidism between the two groups, despite switchers showed a significantly lower time-to-remission. CONCLUSIONS: Conversion of Hashimoto Thyroiditis towards Graves' disease is a rare phenomenon which can occur almost at any time after the development of autoimmune hypothyroidism. Our findings suggest active surveillance of hypothyroid patients who require frequent reduction of levothyroxine during follow up and testing for TSHR antibodies in these patients.