Thyroid hormone action and liver disease, a complex interplay.

Thyroid hormone action is involved in virtually all physiological processes. It is well known that the liver and thyroid are intimately linked, with thyroid hormone playing important roles in de novo lipogenesis, beta-oxidation (fatty acid oxidation), cholesterol metabolism, and carbohydrate metabolism. Clinical and mechanistic research studies have shown that thyroid hormone can be involved in chronic liver diseases, including alcohol-associated or NAFLD and HCC. Thyroid hormone action and synthetic thyroid hormone analogs can exert beneficial actions in terms of lowering lipids, preventing chronic liver disease and as liver anticancer agents. More recently, preclinical and clinical studies have indicated that some analogs of thyroid hormone could also play a role in the treatment of liver disease. These synthetic molecules, thyromimetics, can modulate lipid metabolism, particularly in NAFLD/NASH. In this review, we first summarize the thyroid hormone signaling axis in the context of liver biology, then we describe the changes in thyroid hormone signaling in liver disease and how liver diseases affect the thyroid hormone homeostasis, and finally we discuss the use of thyroid hormone-analog for the treatment of liver disease.

Proton Pump Inhibitors Do Not Affect the Bioavailability of a Novel Liquid Formulation of Levothyroxine.

OBJECTIVE: This study evaluates the impact of a representative proton pump inhibitor (PPI) (omeprazole), administered simultaneously or staggered, on the pharmacokinetics of levothyroxine (LT4) solution (Tirosint-SOL). METHODS: This was a randomized, 3-way crossover, comparative bioavailability study in 36 healthy adults under fasting conditions. Omeprazole 40 mg delayed-release capsule was administered once daily from Day 1 to 6 (mornings, Treatment-A; evenings, Treatment-B; none, Treatment-C) to increase and stabilize gastric pH. In the morning of Day 5, a single dose of LT4 solution 600 mcg was administered. Blood samples were collected 0 to 48 hours post-LT4 administration. Noncompartmental pharmacokinetic parameters were calculated for total serum thyroxine using baseline-corrected data. Maximum concentration (Cmax) and area under the concentration-time curve (AUC0-48) were included in an analysis of variance to obtain geometric mean ratios and 90% confidence intervals. RESULTS: For both comparisons (A/C and B/C), geometric mean ratios and 90% confidence intervals for all parameters were within the equivalence boundaries (80%-125%), indicating bioequivalence: for A/C, AUC0-48 98.98% [94%-104%], and Cmax 91.68% [87%-97%]; for B/C, AUC0-48 98.94% [95%-103%], and Cmax 94.90% [90%-100%]. Median Tmax (time associated with Cmax) was similar across treatments. CONCLUSION: This study demonstrated that Tirosint-SOL bioavailability is unaffected by coadministration of a representative PPI, given simultaneously or staggered by about 12 hours, compared to administration of LT4 solution alone. For hypothyroid patients on PPI therapy, administration of LT4 solution may reduce variations in thyroid stimulating hormone levels related to intermittent use of acid-reducing drugs and consequently the need for dose adjustments.

Differential fuel utilization in liver transplant recipients and its relationship with non-alcoholic fatty liver disease.

Metabolic flexibility is the ability to match biofuel availability to utilization. Reduced metabolic flexibility, or lower fatty acid (FA) oxidation in the fasted state, is associated with obesity. The present study evaluated metabolic flexibility after liver transplantation (LT). METHODS: Patients receiving LT for non-alcoholic steatohepatitis (NASH) (n = 35) and non-NASH (n = 10) were enrolled. NASH was chosen as these patients are at the highest risk of metabolic complications. Metabolic flexibility was measured using whole-body calorimetry and expressed as respiratory quotient (RQ), which ranges from 0.7 (pure FA oxidation) to 1.0 is (carbohydrate oxidation). RESULTS: The two cohorts were similar except for a higher prevalence of obesity and diabetes in the NASH cohort. Post-prandially, RQ increased in both cohorts (i.e. greater carbohydrate utilization) but peak RQ and time at peak RQ was higher in the NASH cohort. Fasting RQ in NASH was significantly higher (0.845 vs. 0.772, p < .001), indicative of impaired FA utilization. In subgroup analysis of the NASH cohort, body mass index but not liver fat content (MRI-PDFF) was an independent predictor of fasting RQ. In NASH, fasting RQ inversely correlated with fat-free muscle volume and directly with visceral adipose tissue. CONCLUSION: Reduced metabolic flexibility in patients transplanted for NASH cirrhosis may precede the development of non-alcoholic fatty liver disease after LT.

Time of eating and cardiorespiratory fitness in patients with heart failure with preserved ejection fraction and obesity.

BACKGROUND AND AIMS: Our objective was to examine the impact of caloric intake before or after the mean time of evening meal on cardiorespiratory fitness (CRF) in patients with heart failure with preserved ejection fraction (HFpEF) and obesity. METHODS AND RESULTS: Twelve patients with HFpEF and obesity completed a cardiorespiratory exercise test to measure CRF, defined as peak oxygen consumption (VO2). Three five-pass 24-h dietary recalls were performed for each participant and mean evening meal time was determined for each participant individually as well as the group. Participants were divided into those who ate before (Group I) and after (Group II) the mean time of evening meal, 7:25 PM. Peak VO2 and exercise time were significantly greater in Group II compared to Group I, moreover, delaying time of evening meal was associated with greater peak VO2. CONCLUSION: Caloric intake after the mean time of evening meal was associated with better CRF in patients with HFpEF and concomitant obesity. Later nutrient intake may help prevent fasting related stress associated with cardiac metabolic disturbances present in HFpEF. Based on these findings, prospective trials aimed at examining the effects of later evening meal times in patients with HFpEF and obesity are warranted.

The effects of canagliflozin compared to sitagliptin on cardiorespiratory fitness in type 2 diabetes mellitus and heart failure with reduced ejection fraction: The CANA-HF study.

BACKGROUND: Canagliflozin reduces hospitalizations for heart failure (HF) in type 2 diabetes mellitus (T2DM). Its effect on cardiorespiratory fitness and cardiac function in patients with established HF with reduced ejection fraction (HFrEF) is unknown. METHODS: We conducted a double-blind randomized controlled trial of canagliflozin 100 mg or sitagliptin 100 mg daily for 12 weeks in 88 patients, and measured peak oxygen consumption (VO2 ) and minute ventilation/carbon dioxide production (VE/VCO2 ) slope (co-primary endpoints for repeated measure ANOVA time_x_group interaction), lean peak VO2 , ventilatory anaerobic threshold (VAT), cardiac function and quality of life (ie, Minnesota Living with Heart Failure Questionnaire [MLHFQ]), at baseline and 12-week follow-up. RESULTS: The study was terminated early due to the new guidelines recommending canagliflozin over sitagliptin in HF: 17 patients were assigned to canagliflozin and 19 to sitagliptin, total of 36 patients. There were no significant changes in peak VO2 and VE/VCO2 slope between the two groups (P = .083 and P = .98, respectively). Canagliflozin improved lean peak VO2 (+2.4 mL kgLM-1 min-1 , P = .036), VAT (+1.5 mL kg-1 min-1 , P = .012) and VO2 matched for respiratory exchange ratio (+2.4 mL Kg-1 min-1 , P = .002) compared to sitagliptin. Canagliflozin also reduced MLHFQ score (-12.1, P = .018). CONCLUSIONS: In this small and short-term study of patients with T2DM and HFrEF, interrupted early after only 36 patients, canagliflozin did not improve the primary endpoints of peak VO2 or VE/VCO2 slope compared to sitagliptin, while showing favourable trends observed on several additional surrogate endpoints such as lean peak VO2 , VAT and quality of life.

Prevalence and Severity of Nonalcoholic Fatty Liver Disease Among Caregivers of Patients With Nonalcoholic Fatty Liver Disease Cirrhosis.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, affecting nearly 1 in 3 Americans.1 Nonalcoholic steatohepatitis (NASH), the clinically aggressive variant of NAFLD, has a propensity of fibrosis progression and increased risk of cirrhosis and hepatocellular carcinoma. NASH-related cirrhosis is now the most rapidly growing indication for liver transplantation (LT).2 Disease recurrence and progression to advanced fibrosis after LT are high3; however, the key contributors of these are unknown. We hypothesized that patients with NASH cirrhosis reside in a microenvironment conducive to not only development of NASH but also fibrosis progression, which likely persist after LT and contribute to disease recurrence. The hypothesis was tested by performing vibration-controlled transient elastography (VCTE) in primary caregivers and cohabitants of patients with decompensated cirrhosis awaiting LT.

A novel role for PTK2B in cultured beige adipocyte differentiation.

Adipocyte differentiation is a tightly regulated process which requires the sequential and organized expression of numerous genes and proteins. Phosphorylation of cytoplasmic proteins and key transcription factors represents a critical regulatory mechanism of the process leading to adipocyte maturation and modulation of associated metabolic pathways. Despite the recognition of the importance of protein phosphorylation in adipocyte biology, relatively little is known about the role of specific kinases in thermogenic (brown or beige) adipocyte differentiation and function. In this study, we demonstrate that the non-receptor protein tyrosine kinase 2 beta (PTK2B) plays a critical role in murine beige adipocyte differentiation. We observed that PTK2B protein expression is associated with beige adipocyte differentiation in cultured, immortalized, inguinal stromal vascular fraction cells. CRISPR/Cas9-mediated knock-out of Ptk2b results in non-differentiating white adipocytes, and differentiated beige adipocytes with significantly reduced thermogenic gene and protein expression, enlarged lipid droplet size, and altered mitochondrial respiration. Together, our data in a cell culture system provides evidence for a role of PTK2B in the differentiation of murine beige adipocytes.

Utilization of aspirin and statin in management of coronary artery disease in patients with cirrhosis undergoing liver transplant evaluation.

Coronary artery disease (CAD) assessment is a vital part of liver transplantation (LT) evaluation, as it allows for identification and medical optimization prior to transplantation. Although aspirin and statins are standard of care for CAD, they are not universally used in cirrhosis due to concerns about adverse events. Per protocol, coronary angiography was performed as part of the LT evaluation in all patients over the age of 50 years or with CAD risk factors, even if they were younger than 50. Optimal CAD medical management was defined as the use of both statin and aspirin, unless a contraindication was documented. Impact of these medications on hepatic decompensation, renal function, gastrointestinal bleeding, and need for transfusion was evaluated. CAD was detected in 84/228 (36.8%) patients. Lipid profile was similar in patients with and without CAD. In patients with CAD, statins were started in 19 (23%), while aspirin was used in 30 (36%) patients. In patients with obstructive or multivessel CAD, statin therapy was used only in 41% and 65%, respectively. Statins were more likely to be prescribed in patients with diabetes (32% versus 15%, P = 0.05) and history of dyslipidemia (38% versus 15%, P = 0.02). Use of statin therapy was not linked to hepatic decompensation, hospitalization, or rise in Model for End-Stage Liver Disease (MELD). Similarly, use of aspirin therapy was not associated with increased risk acute variceal hemorrhage, gastrointestinal bleeding, or worsening anemia. In conclusion, in decompensated cirrhosis, lipid profile alone is unable to risk stratify patients with CAD. Statin and aspirin appear to be safe. However, they are significantly underutilized for the management of CAD in this patient population. Liver Transplantation 24 872-880 2018 AASLD.

STAT3 suppresses Wnt/ß-catenin signaling during the induction phase of primary Myf5+ brown adipogenesis.

Thermogenic fat is a promising target for new therapies in diabetes and obesity. Understanding how thermogenic fat develops is important to develop rational strategies to treat obesity. Previously, we have shown that Tyk2 and STAT3, part of the JAK-STAT pathway, are necessary for proper development of classical brown fat. Using primary preadipocytes isolated from newborn mice we demonstrate that STAT3 is required for differentiation and robust expression of Uncoupling Protein 1 (UCP1). We also confirm that STAT3 is necessary during the early induction stage of differentiation and is dispensable during the later terminal differentiation stage. The inability of STAT3-/- preadipocytes to differentiate can be rescued using Wnt ligand secretion inhibitors when applied during the induction stage. Through chemical inhibition and RNAi, we show that it is the canonical ß-catenin pathway that is responsible for the block in differentiation; inhibition or knockdown of ß-catenin can fully rescue adipogenesis and UCP1 expression in the STAT3-/- adipocytes. During the induction stage, Wnts 1, 3a, and 10b have increased expression in the STAT3-/- adipocytes, potentially explaining the increased levels and activity of ß-catenin. Our results for the first time point towards an interaction between the JAK/STAT pathway and the Wnt/ß-catenin pathway during the early stages of in-vitro adipogenesis.

Increased oxidative metabolism in the Li-Fraumeni syndrome.

There is growing evidence that alterations in metabolism may contribute to tumorigenesis. Here, we report on members of families with the Li-Fraumeni syndrome who carry germline mutations in TP53, the gene encoding the tumor-suppressor protein p53. As compared with family members who are not carriers and with healthy volunteers, family members with these mutations have increased oxidative phosphorylation of skeletal muscle. Basic experimental studies of tissue samples from patients with the Li-Fraumeni syndrome and a mouse model of the syndrome support this in vivo finding of increased mitochondrial function. These results suggest that p53 regulates bioenergetic homeostasis in humans. (Funded by the National Heart, Lung, and Blood Institute and the National Institutes of Health; ClinicalTrials.gov number, NCT00406445.).

Midkine concentrations in fine-needle aspiration of benign and malignant thyroid nodules.

CONTEXT: The primary preoperative method for distinguishing malignant from benign thyroid nodules is fine-needle aspiration (FNA) cytology, but it is frequently inconclusive. Midkine (MDK) is a heparin-binding growth factor, which is overexpressed in papillary thyroid carcinoma (PTC). OBJECTIVE: We measured MDK concentrations in FNA samples from benign and malignant thyroid nodules to explore the possibility that MDK measurement might aid in the evaluation of thyroid nodules. DESIGN: 35 subjects underwent preoperative FNA of 45 thyroid nodules, followed by thyroidectomy, providing a histological diagnosis. FNA needle contents were first expressed for cytology, and then, the needle was washed with buffer for immunoassay. In 46 subjects without preoperative FNA samples, FNA was performed ex vivo on 62 nodules within surgically excised thyroid tissue. MEASUREMENTS: MDK was measured using a high-sensitivity sandwich ELISA and normalized to thyroglobulin (Tg) concentration in the sample to adjust for tissue content in the aspirate. RESULTS: The MDK/Tg ratio was higher in 18 PTCs than in 87 benign nodules (204 ± 106 vs 1·2 ± 0·3 ng/mg, mean ± SEM, P < 0·001). Using a threshold of 10 ng/mg, the sensitivity and specificity of the MDK/Tg ratio for diagnosis of PTC were 67% and 99%, respectively. All follicular variant PTCs had a MDK/Tg ratio <10 ng/mg. CONCLUSIONS: The findings indicate that, in FNA samples, the MDK/Tg ratio in PTC is greater than in benign thyroid nodules, raising the possibility that this approach might provide adjunctive diagnostic or prognostic information to complement existing approaches.

Thyroid Hormone Mediated Modulation of Energy Expenditure.

Thyroid hormone (TH) has diverse effects on mitochondria and energy expenditure (EE), generating great interest and research effort into understanding and harnessing these actions for the amelioration and treatment of metabolic disorders, such as obesity and diabetes. Direct effects on ATP utilization are a result of TH's actions on metabolic cycles and increased cell membrane ion permeability. However, the majority of TH induced EE is thought to be a result of indirect effects, which, in turn, increase capacity for EE. This review discusses the direct actions of TH on EE, and places special emphasis on the indirect actions of TH, which include mitochondrial biogenesis and reduced metabolic efficiency through mitochondrial uncoupling mechanisms. TH analogs and the metabolic actions of T2 are also discussed in the context of targeted modulation of EE. Finally, clinical correlates of TH actions on metabolism are briefly presented.

Wnt/ß-catenin signaling is differentially regulated by Gα proteins and contributes to fibrous dysplasia.

Skeletal dysplasias are common disabling disorders characterized by aberrant growth of bone and cartilage leading to abnormal skeletal structures and functions, often attributable to defects in skeletal progenitor cells. The underlying molecular and cellular mechanisms of most skeletal dysplasias remain elusive. Although the Wnt/ß-catenin signaling pathway is required for skeletal progenitor cells to differentiate along the osteoblastic lineage, inappropriately elevated levels of signaling can also inhibit bone formation by suppressing osteoblast maturation. Here, we investigate interactions of the four major Gα protein families (Gα(s), Gα(i/o), Gα(q/11), and Gα(12/13)) with the Wnt/ß-catenin signaling pathway and identify a causative role of Wnt/ß-catenin signaling in fibrous dysplasia (FD) of bone, a disease that exhibits abnormal differentiation of skeletal progenitor cells. The activating Gα(s) mutations that cause FD potentiated Wnt/ß-catenin signaling, and removal of Gα(s) led to reduced Wnt/ß-catenin signaling and decreased bone formation. We further show that activation of Wnt/ß-catenin signaling in osteoblast progenitors results in an FD-like phenotype and reduction of ß-catenin levels rescued differentiation defects of FD patient-derived stromal cells. Gα proteins may act at the level of ß-catenin destruction complex assembly by binding Axin. Our results indicate that activated Gα proteins differentially regulate Wnt/ß-catenin signaling but, importantly, are not required core components of Wnt/ß-catenin signaling. Our data suggest that activated Gα proteins are playing physiologically significant roles during both skeletal development and disease by modulating Wnt/ß-catenin signaling strength.

Insulin Edema Associated With Glargine.

Insulin edema is a poorly understood complication of insulin therapy. It has been reported in patients with both type 1 and 2 diabetes mellitus and typically occurs in patients with newly diagnosed or poorly controlled diabetes mellitus either after initiation or intensification of insulin therapy. A 20-year-old man presented with anorexia, polydipsia, and weight loss. Serum glucose on admission was 824 mg/dL (45.8 mmol/L) and hemoglobin A1c was >14.0. Additional workup was notable for positive anti-IA2 antibodies and low C-peptide of 0.5 ng/mL (1.1-4.4 ng/mL). He was diagnosed with type 1 diabetes mellitus and was started on insulin therapy with glargine and lispro. Within 4 days after insulin initiation, he developed bilateral leg swelling and reported a 25-pound (11.3-kg) weight gain over the next 10 days. After excluding other systemic causes of edema such as heart failure, renal failure, and liver failure, a diagnosis of insulin edema was made. Insulin glargine was switched to insulin degludec. Complete resolution of edema occurred within 3 days of switching the insulins. Insulin edema is a diagnosis of exclusion. Insulin's role in renal sodium handling, vasodilation, and increased vascular permeability have been postulated as possible mechanisms. Clinicians should be aware of this rare complication.

Overexpression of ORMDL3 confers sexual dimorphism in diet-induced non-alcoholic steatohepatitis.

OBJECTIVE: The bioactive sphingolipid metabolites ceramide and sphingosine-1-phosphate (S1P) accumulate with overnutrition and have been implicated in non-alcoholic steatohepatitis (NASH) development. ORMDL3, a negative regulator of the rate-limiting step in ceramide biosynthesis, has been identified as an obesity-related gene. Therefore, we assessed the role of ORMDL3 in diet-induced obesity and development of NASH. METHODS: Globally overexpressing Ormdl3-Flag transgenic mice (ORMDL3TG) were fed a western high-fat, carbohydrate and cholesterol enriched diet, with high fructose-glucose drinking water. Physiological, biochemical and sphingolipidomic analyses were employed to measure the effect of ORMDL3 overexpression on NASH development. RESULTS: ORMDL3TG male but not female mice fed a western high-fat diet and sugar water had exacerbated adipocyte hypertrophy together with increased severity of white adipose inflammation and fibrosis. Hepatic steatosis, dyslipidemia, impaired glucose homeostasis, hyperinsulinemia, and insulin resistance were significantly more severe only in obese ORMDL3TG male mice that accompanied dramatic liver fibrosis, inflammation, and formation of hepatic crown-like structures, which are unique features of human and murine NASH. Obesogenic diet induces ORMDL expression in male mice but reduces it in females. Mechanistically, overexpression of Ormdl3 lowered the levels of S1P and ceramides only in obese female mice and antithetically increased them in tissues of obese males. ORMDL3TG male mice exhibited a much greater induction of the UPR, propagating ER stress that contributed to their early development of NASH. CONCLUSIONS: This study uncovered a previously unrecognized role for ORMDL3 in sexual dimorphism important for the development and progression of NASH.

Adipose tissue-selective ablation of ADAM10 results in divergent metabolic phenotypes following long-term dietary manipulation.

A Disintegrin And Metalloproteinase domain-containing protein 10 (ADAM10), is involved in several metabolic and inflammatory pathways. We speculated that ADAM10 plays a modulatory role in adipose tissue inflammation and metabolism. To this end, we studied adipose tissue-specific ADAM10 knock-out mice (aKO). While young, regular chow diet-fed aKO mice showed increased insulin sensitivity, following prolonged (33 weeks) high-fat diet (HFD) exposure, aKO mice developed obesity and insulin resistance. Compared to controls, aKO mice showed less inflammatory adipokine profile despite the significant increase in adiposity. In brown adipose tissue, aKO mice on HFD had changes in CD8+ T cell populations indicating a lesser inflammatory pattern. Following HFD, both aKO and control littermates demonstrated decreased adipose tissue pro-inflammatory macrophages, and increased anti-inflammatory accumulation, without differences between the genotypes. Collectively, our observations indicate that selective deletion of ADAM10 in adipocytes results in a mitigated inflammatory response, leading to increased insulin sensitivity in young mice fed with regular diet. This state of insulin sensitivity, following prolonged HFD, facilitates energy storage resulting in increased fat accumulation which ultimately leads to the development of a phenotype of obesity and insulin resistance. In conclusion, the data indicate that ADAM10 has a modulatory effect of inflammation and whole-body energy metabolism.

Critical Approach to Hypothyroid Patients With Persistent Symptoms.

Hypothyroidism is a common condition, and numerous studies have been published over the last decade to assess the potential risks associated with this disorder when inappropriately treated. The standard of care for treatment of hypothyroidism remains levothyroxine (LT4) at doses to achieve biochemical and clinical euthyroidism. However, about 15% of hypothyroid patients experience residual hypothyroid symptoms. Some population-based studies and international population-based surveys have confirmed dissatisfaction with LT4 treatment in some hypothyroid patients. It is well established that hypothyroid patients treated with LT4 exhibit higher serum thyroxine:triiodothyronine ratios and can have a persistent increase in cardiovascular risk factors. Moreover, variants in deiodinases and thyroid hormone transporter genes have been associated with subnormal T3 concentrations, persistent symptoms in LT4-treated patients, and improvement in response to the addition of liothyronine to LT4 therapy. The American (ATA) and European Thyroid Association (ETA) guidelines have recently evolved in their recognition of the potential limitations of LT4. This shift is reflected in prescribing patterns: Physicians' use of combination therapy is prevalent and possibly increasing. Randomized clinical trials have recently been published and, while they have found no improvement in treating hypothyroid patients, a number of important limitations did not allow generalizability. Meta-analyses have reported a preference rate for combination therapy in 46.2% hypothyroid patients treated with LT4. To promote discussions about an optimal study design, the ATA, ETA, and British Thyroid Association have recently published a consensus document. Our study provides a useful counterpoint on the controversial benefits of treating hypothyroid patients with combination therapy.

Unexplained Cachexia as a Presenting Symptom of Pheochromocytoma in a Geriatric Patient.

Pheochromocytomas are rare neuroendocrine tumors that may secrete catecholamines, resulting in a wide array of clinical symptoms. While patients classically present with hypertension, headache, diaphoresis, and flushing, these symptoms are present in only 40% of cases. Here, we describe a 70-year-old woman whose predominant symptom was unexplained severe weight loss over a 12-month period associated with fatigue, anxiety, and palpitations at her endocrinologist and geriatrician visits. Diagnostic imaging was performed to assess for malignancy and demonstrated a 2.0 cm × 2.0 cm left adrenal mass. The diagnosis of pheochromocytoma was confirmed by elevated plasma normetanephrine levels. After a 2-week alpha blockade with doxazosin, the patient underwent robotic left adrenalectomy. Following surgery, the patient regained weight, and her hypertension also improved significantly. We hope this uncommon clinical presentation in an older adult characterized by weight loss and frailty will increase the awareness of atypical pheochromocytoma symptomatology, particularly in older individuals.

Efficacy of Levothyroxine Sodium Soft Gelatin Capsules in Thyroidectomized Patients Taking Proton Pump Inhibitors: An Open-Label Study.

Background: Treatment with proton pump inhibitors (PPIs) and antacids affects the gastrointestinal absorption of levothyroxine sodium (LT4) tablets. Patients with hypothyroidism taking LT4 and PPIs or antacids, thus, require appropriate monitoring. The objective of this study was to determine whether a soft gelatin capsule of LT4 (Tirosint®) would obviate the effect of PPIs on LT4 absorption. The objective was achieved by assessing the effects of a switch from a conventional LT4 tablet form to the same dose as soft capsules in thyroidectomized patients on treatment with LT4 and PPIs. Methods: Patients with history of hypothyroidism due to total thyroidectomy on stable treatment with LT4 tablets, and with gastrointestinal disease treated with PPIs, were switched to a 12-week treatment with Tirosint at the same dose of the LT4 tablets, while maintaining treatment with PPIs. Serum thyrotropin (TSH) levels were the primary endpoint of the study. Secondary efficacy endpoints were: serum levels of free thyroxine (fT4), total thyroxine (TT4), free triiodothyronine (fT3), total triiodothyronine (TT3), creatine-phosphokinase (CPK), sex-hormone binding globulin, ferritin, angiotensin converting enzyme, and a lipid panel. Results: Forty-seven patients (36 females and 11 males, mean age 55.4 years) were enrolled and 45 of them completed the study (2 patients withdrew consent). During treatment with Tirosint, mean TSH levels demonstrated a statistically significant decrease (mean changes from baseline: -0.32 mIU/L at week 6 and -0.68 mIU/L at week 12) and concomitant increases in thyroid hormone (TH) levels from baseline to week 12, which were statistically significant for fT3 and TT3 (mean changes from baseline: 0.26 pmol/L and 0.10 nmol/L, respectively). Significant decreases of serum low-density lipoprotein, total cholesterol, and CPK levels were observed at week 12. No signs/symptoms arose during the study that could be specifically correlated to either hypo- or hyperthyroidism. Conclusions: In thyroidectomized patients taking PPIs and replacement LT4, a switch from conventional LT4 tablets to LT4 soft capsules at the same dose was associated with a significant decrease in TSH and increase in TH, indicating that LT4 absorption may be less affected by PPIs when given in the form of soft capsules. Clinical Trial Registration: NCT03094416.

Small-molecule agonists for the thyrotropin receptor stimulate thyroid function in human thyrocytes and mice.

Seven-transmembrane-spanning receptors (7TMRs) are prominent drug targets. However, small-molecule ligands for 7-transmembrane-spanning receptors for which the natural ligands are large, heterodimeric glycoprotein hormones, like thyroid-stimulating hormone (TSH; thyrotropin), have only recently been reported, and none are approved for human use. We have used quantitative high-throughput screening to identify a small-molecule TSH receptor (TSHR) agonist that was modified to produce a second agonist with increased potency. We show that these agonists are highly selective for human TSHR versus other glycoprotein hormone receptors and interact with the receptor's serpentine domain. A binding pocket within the transmembrane domain was defined by docking into a TSHR homology model and was supported by site-directed mutagenesis. In primary cultures of human thyrocytes, both TSH and the agonists increase mRNA levels for thyroglobulin, thyroperoxidase, sodium iodide symporter, and deiodinase type 2, and deiodinase type 2 enzyme activity. Moreover, oral administration of the agonist stimulated thyroid function in mice, resulting in increased serum thyroxine and thyroidal radioiodide uptake. Thus, we discovered a small molecule that activates human TSHR in vitro, is orally active in mice, and could be a lead for development of drugs to use in place of recombinant human TSH in patients with thyroid cancer.