Medical treatment of thyrotoxicosis.

Medical treatment is the primary therapeutic option for thyrotoxicosis/hyperthyroidism. Two groups of causes of thyrotoxicosis (i.e. thyrotoxicosis with hyperthyroidism and thyrotoxicosis without hyperthyroidism) need to be considered for therapeutic reasons. Herein we provide an updated review on the role of conventional medical therapies (i.e. ß-blockers, antithyroid drugs [ATDs], corticosteroids, inorganic iodide, perchlorate, cholecystographic agents, lithium, cholestyramine) in the main causes of thyrotoxicosis, starting from the rationale subtending their clinical application.

Radioiodine therapy of thyroid autonomy.

Radioiodine therapy (RIT) of thyroid functional autonomy (TFA) is rapidly evolving, though it has been recognized for decades as a very effective treatment of toxic nodular varieties. Indeed, TFA is a frequent cause of persistent subclinical hyperthyroidism, which should be regarded as a new metabolic syndrome, with well-established adverse cardio-vascular consequences. Sensitive TSH assays and multiparametric ultrasounds are not accurate enough to reliably diagnose TFA and identify its main variants, unifocal, multifocal (UFA/MFA) and disseminated autonomy (DISA). Modern diagnostic tools are extensively presented and rely upon Thyroid Scan imaging and quantification. A new relationship allows predicting at baseline, an excess of 123I uptake as compared to the TSH stimulation in compensated TFA. Suppressed TS are useful with either isotope, otherwise. Diagnosis of the DISA variant is presented as compared to Graves' disease. Dosimetry has some specificity in TFA work-up. Indeed, the spatial distribution of the dose is as important as the mean value itself and can be eventually controlled by adjusting the TSH level with the smart use of LT3 or antithyroid drug therapy (ATD). A review of the different ways to determine the target mass from anatomical to functional approaches is presented. Main clinical and dosimetric published results of RIT are summarized according to clinical goals. Endogenous TSH stimulation using an ATD preparation has promising results in reducing big autonomously functioning goiters. Finally, we report preliminary successful results of preventive RIT using short term LT3 suppression in compensated TFA, with low administered activities and low rate of hypothyroidism.

Chromatographic methods development, validation and degradation characterization of the antithyroid drug Carbimazole.

The current paper reports the development and validation of stability-indicating HPLC and HPTLC methods for the separation and quantification of main impurity and degradation product of Carbimazole. The structures of the degradation products formed under stress degradation conditions, including hydrolytic and oxidative, photolytic and thermal conditions, were characterized and confirmed by MS and IR analyses. Based on the characterization data, the obtained degradation product from hydrolytic conditions was found to be methimazole-impurity A of Carbimazole as reported by the British Pharmacopeia and the European Pharmacopeia. A stability-indicating HPLC method was carried out using a Zorbax Eclipse Plus CN column (150 × 4.6 mm i.d, 5 µm particle size) and a mobile phase composed of acetonitrile-0.05 m KH2 PO4 (20: 80, v/v) in isocratic elution, at a flow rate of 1 mL/min. The method was proved to be sensitive for the determination down to 0.5% of Carbimazole impurity A. Additionally, a stability-indicating chromatographic HPTLC method was achieved using cyclohexane-ethanol (9:1, v/v) as a developing system on HPTLC plates F254 with UV detection at 225 nm. The proposed HPLC and HPTLC methods were successfully applied to Carbimazole® tablets with mean percentage recoveries of 100.12 and 99.73%, respectively.

Design, Synthesis, Molecular Modeling, and Biological Evaluation of Novel Thiouracil Derivatives as Potential Antithyroid Agents.

Hyperthyroidism is the result of uncontrolled overproduction of the thyroid hormones. One of the mostly used antithyroid agents is 6-n-propyl-2-thiouracil (PTU). The previously solved X-ray crystal structure of the PTU bound to mammalian lactoperoxidase (LPO) reveals that the LPO-PTU binding site is basically a hydrophobic channel. There are two hydrophobic side chains directed towards the oxygen atom in the C-4 position of the thiouracil ring. In the current study, the structural activity relationship (SAR) was performed on the thiouracil nucleus of PTU to target these hydrophobic side chains and gain more favorable interactions and, in return, more antithyroid activity. Most of the designed compounds show superiority over PTU in reducing the mean serum T4 levels of hyperthyroid rats by 3% to 60%. In addition, the effect of these compounds on the levels of serum T3 was found to be comparable to the effect of PTU treatment. The designed compounds in this study showed a promising activity profile in reducing levels of thyroid hormones and follow up experiments will be needed to confirm the use of the designed compounds as new potential antithyroid agents.

Role of a gitogenin-type steroidal saponin (3-O-ß-d-glucopyranosyl (1→2)-ß-d-glucopyranosyl (1→4)-ß-d-galactopyranoside-25R,5α-spirostane-2α,3ß-diol), isolated from the leaves of Malvastrum coromandelianum in regulating thyrotoxicosis in rats.

The hitherto unknown role of saponin in the regulation of thyrotoxicosis has been revealed in chemically-induced thyrotoxic rats. l-T4 (l-thyroxine) administration at pre-standardized dose of 500-µg/kg body weight for 12days increased the levels of thyroid hormones, enhanced the activity of hepatic 5'-monodeiodinase I (5'DI) and glucose-6-phosphatase (G-6Pase) as well as lipid peroxidation (LPO) with a parallel decrease in the levels of antioxidative enzymes. However, administration of the isolated saponin for 15days ameliorated the T4-induced alterations in serum thyroid hormones, hepatic LPO, G-6-Pase and 5'DI activity, and improved the cellular antioxidant status, indicating its antithyroidal and antioxidative potential. These effects of the test compound were comparable to a reference antithyroid drug, Propylthiouracil (PTU), suggesting that the test saponin may act as a potent anti-thyroid agent.

Antithyroid drugs and their analogues: synthesis, structure, and mechanism of action.

Thyroid hormones are essential for the development and differentiation of all cells of the human body. They regulate protein, fat, and carbohydrate metabolism. In this Account, we discuss the synthesis, structure, and mechanism of action of thyroid hormones and their analogues. The prohormone thyroxine (T4) is synthesized on thyroglobulin by thyroid peroxidase (TPO), a heme enzyme that uses iodide and hydrogen peroxide to perform iodination and phenolic coupling reactions. The monodeiodination of T4 to 3,3',5-triiodothyronine (T3) by selenium-containing deiodinases (ID-1, ID-2) is a key step in the activation of thyroid hormones. The type 3 deiodinase (ID-3) catalyzes the deactivation of thyroid hormone in a process that removes iodine selectively from the tyrosyl ring of T4 to produce 3,3',5'-triiodothyronine (rT3). Several physiological and pathological stimuli influence thyroid hormone synthesis. The overproduction of thyroid hormones leads to hyperthyroidism, which is treated by antithyroid drugs that either inhibit the thyroid hormone biosynthesis and/or decrease the conversion of T4 to T3. Antithyroid drugs are thiourea-based compounds, which include propylthiouracil (PTU), methimazole (MMI), and carbimazole (CBZ). The thyroid gland actively concentrates these heterocyclic compounds against a concentration gradient. Recently, the selenium analogues of PTU, MMI, and CBZ attracted significant attention because the selenium moiety in these compounds has a higher nucleophilicity than that of the sulfur moiety. Researchers have developed new methods for the synthesis of the selenium compounds. Several experimental and theoretical investigations revealed that the selone (C═Se) in the selenium analogues is more polarized than the thione (C═S) in the sulfur compounds, and the selones exist predominantly in their zwitterionic forms. Although the thionamide-based antithyroid drugs have been used for almost 70 years, the mechanism of their action is not completely understood. Most investigations have revealed that MMI and PTU irreversibly inhibit TPO. PTU, MTU, and their selenium analogues also inhibit ID-1, most likely by reacting with the selenenyl iodide intermediate. The good ID-1 inhibitory activity of PTU and its analogues can be ascribed to the presence of the -N(H)-C(═O)- functionality that can form hydrogen bonds with nearby amino acid residues in the selenenyl sulfide state. In addition to the TPO and ID-1 inhibition, the selenium analogues are very good antioxidants. In the presence of cellular reducing agents such as GSH, these compounds catalytically reduce hydrogen peroxide. They can also efficiently scavenge peroxynitrite, a potent biological oxidant and nitrating agent.

Bracketed Stability Evaluation of Methimazole USP in PLO Gel Mediflo™30 Pre-Mixed.

Extemporaneously compounded Methimazole 1% and 10% in PLO Gel Mediflo™30 Pre-Mixed were studied to assess physical, chemical and microbial stability over time. The formulations were stored at room temperature in tightly closed, light resistant plastic containers. Chemical stability was evaluated using a validated, stability indicating HPLC analysis and physical stability was evaluated through observation of organoleptic appearance and pH measurement at predetermined time points. Lastly, antimicrobial effectiveness testing was conducted per USP <51> guidelines. The results indicate that compounded Methimazole remained within the stability criteria for the duration of the study and can be assigned an extended beyond-use-date of 120 days under the studied conditions.

[Thyrostatic treatment and its adverse effects]. / Tyreostatická liecba a jej neziadúce úcinky.

Antithyroid drugs are relatively simple molecules known as thionamides, which contain a sulfhydryl group and a thiourea moiety within a heterocyclic structure. Propylthiouracil (6- propyl 2- sulfanylidene 1,2,3,4- tetrahydropyrimidin4- one) and methimazole (1- metyl 2,3- dihydro1H imidazole 2- thione) are the antithyroid drugs used in the United States. Methimazole is used in most of Europe and Asia, and carbimazole -  methimazole analogue, is used in the United Kingdom and parts of the former British Commonwealth. Their primary effect is to inhibit thyroid hormone synthesis by interfering with thyroid peroxidase mediated iodination of tyrosine residues in thyroglobulin and is an important step in the synthesis of thyroxine and triiodothyronine. Propylthiouracil (but not methimazole or carbimazole), can block the conversion of thyroxine to triiodothyronine within the thyroid and in peripheral tissues. Antithyroid drugs may have clinically important immunosuppressive effects. Side effects of thionamides are usually mild, serious untoward effects are observed in < 5% of cases, more frequently during the initial phases of treatment, when the drug daily dose is higher.

Synthesis and structural characterization of new Cu(I) complexes with the antithyroid drug 6-n-propyl-thiouracil. study of the Cu(I)-catalyzed intermolecular cycloaddition of iodonium ylides toward benzo[b]furans with pharmaceutical implementations.

The reaction of copper(I) iodide with 6-n-propylthiouracil (ptu) in the presence or absence of the triphenylphosphine (tpp) or tri(p-tolyl)phosphine (tptp) in a 1:1:2 molar ratio forms the mixed ligand Cu(I) complex with formula [CuI(ptu)2](toluene) (1), [CuI(tpp)2(ptu)] (2), and [CuI(tptp)2(ptu)] (3). The complexes have been characterized by FT-IR, (1)H NMR, UV-vis, spectroscopic techniques, and single crystal X-ray crystallography. Two sulfur atoms from two ptu ligands and one iodide form a trigonal geometry around the metal center in 1. Intramolecular interactions through hydrogen bonds lead to a bend ribbon polymeric supramolecular architecture with zigzag conformation. Two phosphorus atoms from two arylphosphines, one sulfur atom, and one iodide anion form a tetrahedron around the copper ion in case of 2 and 3. Intramolecular hydrogen bonding interactions lead to dimerization. Complexes 1-3 and the already known ones with formulas, [(tpSb)2Cu(µ2-I)2Cu(tpSb)2] (4) (tbSb = triphenylstibine), [(tpp)Cu(µ2-I)2Cu(tpp)2] (5), [(tpp)Cu(µ2-Cl)2Cu(tpp)2] (6), [CuCl(tpp)3·(CH3CN)] (7), and [AuCl(tpp)] (8), were used to study their catalytic activity on the intermolecular cycloaddition of iodonium ylides toward benzo[b]furans formation. The results show that both the metal and the ligand type affect the catalytic affinity of the complexes. The highest yield of benzo[b]furan was derived when complexes 2, 3, and 4 were used as catalysts. The mechanism of the Cu(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide has been also thoroughly explored by means of ab initio electronic structure calculation methods, and the results are compared with the experimental ones.

The effect of perchlorate medication on point-of-care testing.

BACKGROUND: To create awareness for mismeasurements of ion-selective electrodes caused by patients' medications and to prevent severe consequences in an intensive care therapy. CASE PRESENTATION: A 73-year-old woman presented with severe carbimazol-induced toxic epidermal necrolysis. After replacement of carbimazol by sodiumperchlorate, we detected a huge discrepancy in the measurement of ionised calcium by two different Point-of-Care (POCT) systems. While Siemens Rapidlab 865 showed a severe hypocalcemia at all times, the Radiometer 600 system first presented a severe hypercalcemia and, in the course of the following days, also a hypocalcemia but with significantly (p < 10 to the -45) higher values than the Rapidlab system. Furthermore, the POCT systems detected a pseudohypocalcemia at times where we think there was a normo- or even hypercalcemia which led to incorrect therapy with excessive substitution of ionised calcium. CONCLUSIONS: The substance sodiumperchlorate, which is well established in Europe for hyperthyreosis therapy, caused malfunctions of analyses of ionised calcium by POCT systems.

Homeopathic and integrative treatment for feline hyperthyroidism--four cases (2006-2010).

Hyperthyroidism is a frequent veterinary problem, particularly in elderly cats. Homeopathic treatment and other integrative modalities were provided for four hyperthyroid cats whose owners did not want conventional treatment. Symptomatic homeopathic treatment with Thyroidinum was helpful in one cat. All cats were prescribed an appropriate individualized homeopathic remedy. All four cats showed resolution of clinical signs; three attained normal thyroid hormone levels. Three cats later received acupuncture and/or herbal medicines; two cats later received symptomatic homeopathic remedies. Two cats are thriving after over 3.5 and 4.25 years of treatment; two were euthanized for unrelated problems after 3 and 4 years of treatment. Homeopathic and complementary therapies avoid the potential side effects of methimazole and surgical thyroidectomy, they are less costly than radioactive iodine treatment, and they provide an option for clients who decline conventional therapies.

Cocrystals of 6-propyl-2-thiouracil: N-H···O versus N-H···S hydrogen bonds.

In order to investigate the relative stability of N-H···O and N-H···S hydrogen bonds, we cocrystallized the antithyroid drug 6-propyl-2-thiouracil with two complementary heterocycles. In the cocrystal pyrimidin-2-amine-6-propyl-2-thiouracil (1/2), C(4)H(5)N(3)·2C(7)H(10)N(2)OS, (I), the `base pair' is connected by one N-H···S and one N-H···N hydrogen bond. Homodimers of 6-propyl-2-thiouracil linked by two N-H···S hydrogen bonds are observed in the cocrystal N-(6-acetamidopyridin-2-yl)acetamide-6-propyl-2-thiouracil (1/2), C(9)H(11)N(3)O(2)·2C(7)H(10)N(2)OS, (II). The crystal structure of 6-propyl-2-thiouracil itself, C(7)H(10)N(2)OS, (III), is stabilized by pairwise N-H···O and N-H···S hydrogen bonds. In all three structures, N-H···S hydrogen bonds occur only within R(2)(2)(8) patterns, whereas N-H···O hydrogen bonds tend to connect the homo- and heterodimers into extended networks. In agreement with related structures, the hydrogen-bonding capability of C=O and C=S groups seems to be comparable.

Antithyroid drugs and their analogues protect against peroxynitrite-mediated protein tyrosine nitration--a mechanistic study.

In this paper, the effect of some commonly used antithyroid drugs and their analogues on peroxynitrite-mediated nitration of proteins is described. The nitration of tyrosine residues in bovine serum albumin (BSA) and cytochrome c was studied by Western blot analysis. These studies reveal that the antithyroid drugs methimazole (MMI), 6-n-propyl-2-thiouracil (PTU), and 6-methyl-2-thiouracil (MTU), which contain thione moieties, significantly reduce the tyrosine nitration of both BSA and cytochrome c. While MMI exhibits good peroxynitrite (PN) scavenging activity, the thiouracil compounds PTU and MTU are slightly less effective than MMI. The S- and Se- methylated compounds show a weak inhibitory effect in the nitration of tyrosine, indicating that the presence of a thione or selone moiety is important for an efficient inhibition. Similarly, the replacement of N-H moiety in MMI by N-methyl or N-m-methoxybenzyl substituents dramatically reduces the antioxidant activity of the parent compound. Theoretical studies indicate that the substitution of N-H moiety by N-Me significantly increases the energy required for the oxidation of sulfur center by PN. However, such substitution in the selenium analogue of MMI increases the activity of parent compound. This is due to the facile oxidation of the selone moiety to the corresponding selenenic and seleninic acids. Unlike N,N'-disubstituted thiones, the corresponding selones efficiently scavenge PN, as they predominantly exist in their zwitterionic forms in which the selenium atom carries a large negative charge.

Interaction of heterocyclic thiols/thiones eliminated from cephalosporins with iodine and its biological implications.

Hydrolysis of beta-lactam antibiotics by beta-lactamases (e.g., metallo-beta-lactamase, mbetal) is one of the major bacterial defense systems. These enzymes can catalyze the hydrolysis of a variety of antibiotics including the latest generation of cephalosporins, cephamycins and imipenem. It is shown in this paper that the thiol/thione moieties eliminated from certain cephalosporins by mbetal-mediated hydrolysis readily react with molecular iodine to produce ionic compounds having S-I bonds. While the reaction of MTT with iodine produced the corresponding disulfide, MDT and DMETT produced the charge-transfer complexes MDT-I(2) and DMETT-I(2), respectively. Addition of two equivalents of I(2) to MDT produced a novel cationic complex having an almost linear S-I(+)-S moiety and I(5)(-) counter anion. However, this reaction appears to be highly solvent dependent. When the reaction of MDT with I(2) was carried out in water, the reaction produced a monocation having I(5)(-), indicating the reactivity of MDT toward I(2) is very similar to that of the most commonly used antithyroid drug methimazole (MMI). In contrast to MMI, MDT and DMETT, the triazine-based compound MTDT acts as a weak donor toward iodine.

Copper(II) complexes of methimazole, an anti Grave's disease drug. Synthesis, characterization and its potential biological behavior as alkaline phosphatase inhibitor.

Methimazole (MeimzH) is an anti-thyroid drug and the first choice for patients with Grave's disease. Two new copper(II) complexes of this drug: [Cu(MeimzH)(2)(NO(3))(2)]*0.5H(2)O and [Cu(MeimzH)(2)(H(2)O)(2)](NO(3))(2)*H(2)O were synthesized and characterized by elemental analysis, dissolution behavior, thermogravimetric analysis and UV-vis, diffuse reflectance, FTIR and EPR spectroscopies. As it is known that copper(II) cation can act as an inhibitor of alkaline phosphatase (ALP), the inhibitory effect of methimazole and its copper(II) complexes on ALP activity has also been investigated.

Thiouracil: Comprehensive profile.

Thiouracil, 2-sulfanylidene-1H-pyrimidin-4-one, has been used as anti-thyroid, coronary vasodilator, and in congestive heart failure. It was found to cause agranulocytosis and it is suspected to be teratogenic and carcinogenic. Owing to its high frequency of adverse reactions, especially agranulocytosis, its use was abandoned in favor of other, less toxic drugs, such as propylthiouracil and methimazole. Thiouracil refers both to a specific molecule consisting of a sulfated uracil and a family of molecules based upon the structure. An important member of this family is propylthiouracil, which is a thiourea antithyroid drug that acts by blocking the production of thyroid hormones; it also inhibits the peripheral deiodination of thyroxine to tri-iodothyronine. This profile is prepared to discuss and explain physical and chemical properties, proprietary and nonproprietary names of thiouracil and propylthiouracil. It also includes uses and applications, methods of preparation, thermal and spectral behavior and methods of analysis. In addition, metabolism, excretion and pharmacology of propylthiouracil are also discussed.

A low-molecular-weight antagonist for the human thyrotropin receptor with therapeutic potential for hyperthyroidism.

Low-molecular-weight (LMW) antagonists for TSH receptor (TSHR) may have therapeutic potential as orally active drugs to block stimulating antibodies (TsAbs) in Graves' hyperthyroidism. We describe an approach to identify LMW ligands for TSHR based on Org41841, a LMW partial agonist for the LH/choriogonadotropin receptor and TSHR. We used molecular modeling and functional experiments to guide the chemical modification of Org41841. We identified an antagonist (NIDDK/CEB-52) that selectively inhibits activation of TSHR by both TSH and TsAbs. Whereas initially characterized in cultured cells overexpressing TSHRs, the antagonist was also active under more physiologically relevant conditions in primary cultures of human thyrocytes expressing endogenous TSHRs in which it inhibited TSH- and TsAb-induced up-regulation of mRNA transcripts for thyroperoxidase. Our results establish this LMW compound as a lead for the development of higher potency antagonists and serve as proof of principle that LMW ligands that target TSHR could serve as drugs in patients with Graves' disease.

Thionamides inhibit the transcription factor nuclear factor-kappaB by suppression of Rac1 and inhibitor of kappaB kinase alpha.

Thionamides, inhibitors of the thyroid peroxidase-mediated iodination, are clinically used in the treatment of hyperthyroidism. However, the use of antithyroid drugs is associated with immunomodulatory effects, and recent studies with thionamide-related heterocyclic thioderivates demonstrated direct anti-inflammatory and immunosuppressive properties. Using primary human T-lymphocytes, we show that the heterocyclic thionamides carbimazole and propylthiouracil inhibit synthesis of the proinflammatory cytokines tumor necrosis factor (TNF)alpha and interferon (IFN)gamma. In addition, DNA binding of nuclear factor (NF)-kappaB, a proinflammatory transcription factor that regulates both TNFalpha and IFNgamma synthesis, and NF-kappaB-dependent reporter gene expression were reduced. Abrogation of NF-kappaB activity was accompanied by reduced phosphorylation and proteolytic degradation of inhibitor of kappaB (IkappaB)alpha, the inhibitory subunit of the NF-kappaB complex. Carbimazole inhibited NF-kappaB via the small GTPase Rac-1, whereas propylthiouracil inhibited the phosphorylation of IkappaBalpha by its kinase inhibitor of kappaB kinase alpha. Methimazole had no effect on NF-kappaB induction, demonstrating that drug potency correlated with the chemical reactivity of the thionamide-associated sulfur group. Taken together, our data demonstrate that thioureylenes with a common, heterocyclic structure inhibit inflammation and immune function via the NF-kappaB pathway. Our results may explain the observed remission of proinflammatory diseases upon antithyroid therapy in hyperthyroid patients. The use of related thioureylenes may provide a new therapeutic basis for the development and application of anti-inflammatory compounds.

Determination of methimazole in urine with the iodine-azide detection system following its separation by reversed-phase high-performance liquid chromatography.

The iodine-azide detection system to determine methimazole following its separation by RP-HPLC is described in this paper. The reaction between iodine and azide ions induced by methimazole was applied as a post-column reaction detection system. Neither extraction nor preconcentration of the sample was necessary. The methimazole standards added to normal urine show that the response of the detector, set at 350 nm (corresponding to unreacted iodine in the post-column iodine-azide reaction), was linear within the concentration range 2-10 nmol/mL of urine. The relative standard deviation values for precision and recovery within the calibration range were from 0.3 to 3.2% and from 97 to 102%, respectively. Limits of detection (LOD) and quantitation (LOQ) were 1 and 2 nmol/mL of urine, respectively. The method was applied to the separation and determination of patient urine samples and the analytical results were satisfactory.

Calorimetric and spectroscopic studies on the interaction of methimazole with bovine serum albumin.

The potential binding interaction(s) of the anti-thyroid drug methimazole (MMZ) with the protein bovine serum albumin (BSA) has been studied using isothermal titration calorimetry (ITC) and UV-Visible, fluorescence and circular dichroism (CD) spectroscopic techniques. The binding of MMZ to BSA has been studied in both the presence and absence of added surfactants. Since, the ITC thermograms show the molar enthalpy of binding of MMZ and BSA to be zero within experimental error, either the enthalpy change of the binding interaction is zero or there is no binding occurring. The CD and the intrinsic fluorescence and life time spectra of BSA were unchanged by the addition of MMZ. This is also indicative of the absence of any significant interaction of MMZ with BSA.