Hepatotoxicity from antithyroid drugs

We review the cases of hepatic injury from propylthiouracil, methimazole and carbimazole in the English language literature and compare them to cases of agranulocytosis in a recent review. The data on hepatotoxicity confirm the findings for agranulocytosis that low-dose methimazole is safer than propylthiouracil and that methimazole toxicity is more common over 40 years old. In contrast, propylthiouracil hepatotoxicity often occurs in younger patients. Most cases of hepatic injury occur in the first few months of drug therapy as with agranulocytosis. The reason that methimazole typically causes cholestatic hepatitis while propylthiouracil causes cytotoxic hepatitis remains unknown.

[Autoimmunity induced by drugs. Immunological characteristics and etiopathogenic hypotheses]

Drug-induced autoimmune diseases have two immunological peculiarities. Firstly, some autoantibodies are present, which are virtually never seen in spontaneous human diseases and may be regarded as specific. This applies to antimitochondria antibody type 3 (anti M3) in the lupus-like syndrome caused by Venocuran, to antimitochondria antibody type 6 (anti M6) in iproniazide-induced hepatitis, to anti-insulin antibody found after treatment with methimazole, and to anti liver/kidney microsome antibody type 2 (anti LKM2) associated with hepatitis induced by tielinic acid. Secondly, a search for other autoantibodies shows that the immune disorder is much more limited than in spontaneous autoimmune diseases. Thus, contrary to myasthenia and idiopathic autoimmune haemolytic anaemia, we never found autoantibodies specifically directed against the thyroid, the stomach or the adrenal gland during treatment with D-penicillamine and alpha-methyldopa. Only some hypotheses may account for these peculiarities. Cross-reaction between drug and autoantigen may occur, but the fact that the antigen-antibody reaction is not inhibited by the drug or its metabolites does not support this explanation. Much more attractive is the "T-cell bypass" theory, according to which autoreacting suppressor T-cells are circumvented by helper T-cells stimulated by the drug-modified autoantigen. In this case, the autoimmune reaction would indicate to which body substance the drug is bound, thus making it immunostimulant, and not a structural similarity between the drug and the autoantigen.

Insulin autoimmunity as a cause of hypoglycemia

"Autoimmune" hypoglycemia is a syndrome consisting of fasting hypoglycemia, hyperinsulinemia, and insulin-binding antibodies in a patient who has never been exposed to exogenous insulin. The stimulus for insulin-antibody formation and the mechanism of the hypoglycemia in this condition remain unknown. Three patients with this rare syndrome had severe hypoglycemia of limited duration. Two had received a drug containing a sulfhydryl group (methimazole and penicillamine) as treatment for an autoimmune disorder (Graves' disease and rheumatoid arthritis, respectively). A third patient who underwent surgery for a suspected insulinoma was found to have pancreatic beta cell hyperplasia. Drugs containing a sulfhydryl group may have a role in the etiology of the syndrome. Additionally, our findings suggest a relationship between circulating insulin antibodies and beta cell hyperplasia.

Antithyroid drugs

Over the past four decades, a great deal has been learned about the pharmacology and mechanisms of action of antithyroid drugs. Their ability to inhibit hormone biosynthesis involves complex interactions with thyroid peroxidase and thyroglobulin, many of which are still poorly understood. Their spectrum of activity is much wider than previously thought, and a number of clinically important extrathyroidal actions have been identified. Despite a greater appreciation for the intricacies of antithyroid-drug pharmacology, controversies still surround the use of these agents in the treatment of thyrotoxicosis. These controversies are apt to continue until the pathophysiology of Graves' disease is fully elucidated.

Fixed drug eruptions. A study of 20 occurrences in Singapore

Twenty occurrences of fixed drug eruptions (FDE) were studied. Of these, 12 were due to tetracyclines and 4 were due to analgesics (3 from pyrazolone derivatives and 1 from acetylsalicylic acid). Sixteen of the patients had less than 10 lesions each. The lips were affected in eight instances, and therefore seem preferentially involved. At presentation, seven patients were unaware of a drug relationship to their condition. A comparison of six reported series (including this one) revealed that the causative drugs varied over the years 1956-1983 as well as by region.

Maternal hyperthyroidism and congenital malformation in the offspring

Six hundred and forty-three neonates from mothers with Graves' disease were examined for major malformations of external organs to compare the influence of maternal hyperthyroidism vs. ingestion of methimazole (MMI) during the first trimester on the incidence of congenital malformations. The subjects were divided into four groups according to maternal therapy and thyroid status during the first trimester as follows: (1) infants whose mothers did not receive MMI and were hyperthyroid (Group 1), (2) infants whose mothers did not receive MMI and were euthyroid (Group 2), (3) infants whose mothers received MMI and were hyperthyroid (Group 3) and (4) infants whose mothers received MMI and were euthyroid (Group 4). The prevalence of malformed infants in these four groups was 6.0% (three of 50), 0.3% (one of 350), 1.7% (two of 117) and 0.0% (none of 126), respectively. The incidence in Group 1 was significantly higher than that in Group 2 (P less than 0.01). There was no discernible dose dependency of MMI on the occurrence of malformations. These findings suggest that maternal uncontrolled hyperthyroidism may cause congenital malformations and that the beneficial role of MMI treatment outweighs its teratogenic effect, if any.

Low-dosed antithyroid drug monotherapy in hyperthyroidism

In the antithyroid drug therapy, an initial treatment with low doses (10-15 mg) of methimazole (MMI) leads to satisfactory improvement in nearly all cases and even 5 mg MMI are sufficient in more than 50% of all patients. Additional intake of thyroid hormones (Th) is not necessary, if the MMI-dosage is reduced accordingly to the individual course of treatment. Consequent follow -up is to recommend anyway, particularly under the higher MMI-doses and in the first time, respectively. Consecutive measurement of total T-3 helps in assessment of euthyroidism under treatment, whereas the response to MMI is indicated more correct by total T-4. Serial determinations of serum-TSH are very helpful to decide about the cessation of treatment. If any goitre growth occurs, it seems not to be TSH-mediated in every case. Skin reactions as side-effect of high MMI-doses can be prevented by use of low doses.

[Thyrostatic therapy of hyperthyroidism with special reference to drug side effects]

In discussing undesirable therapy effects by thyrostatics one must issue from the fact that the possible side effects have a different genesis and appear in different frequency. While pharmacodynamically caused therapy effects are generally to be avoided, when considering the pathophysiology of the regulation of the thyroid gland, this is not the case as to allergic side effects and only to a limited extent with regard to toxic side effects. Allergic side effects abruptly and suddenly appear and do not show any dependence on dosage. But for the greater part these side effects are harmless. Severe side effects are nearly without exception of toxic genesis. The decrease of the initial dose and the early transition to a still effective maintenance dose reduce the possibility of toxic complications. In case that side effects lead to a discontinuation of the corresponding thyrostatic, a change to a thyrostatic of another chemical group is possible and necessary.

Glucagon binding autoantibodies in a patient with hyperthyroidism treated with methimazole

A 47-yr-old woman who had previously received methimazole (MMI) treatment for hyperthyroidism was found to have glucagon binding autoantibodies in plasma. She had never received glucagon. The binding substances were detected in plasma at the time of a glucagon RIA. [125I]Glucagon binding was inhibited only by porcine glucagon and porcine glicentin, and dissociated at acid pH. The substances proved to be glucagon binding antibodies (immunoglobulin G, L-chain K-type), as determined by ammonium sulfate and radioprecipitation. There were no clinical manifestations related the presence of these autoantibodies. In a survey of 91 patients with thyroid disease, 3 patients whose plasma bound [125I]glucagon were identified among 41 with hyperthyroidism who were receiving MMI treatment. Such binding was not found in plasma from untreated hyperthyroid patients, those receiving propylthiouracil or those with chronic thyroiditis. These findings suggest that the development of glucagon antibodies in hyperthyroidism may be associated with MMI treatment.

[Side effects of antithyroid drugs]

In order to investigate the incidence of side effects of antithyroid drugs and to study if there were any factors related to the onset of the side effects, clinical and laboratory findings were examined in 71 untreated Graves' patients. The overall incidence was 28.2% among 71 cases who were initially administered methimazole or propylthiouracil. The incidences were 23.2% (13 of 56 cases) for methimazole and 46.7% (7 of 15 cases) for propylthiouracil, respectively, which were significantly higher than those previously reported. Seventeen of 20 cases with side effects under the drug of first choice were administered the another antithyroid drug. Four of 17 (23.5%) cases successively had side effects. The side effects were observed within 1.5 months of administration of less than 150 tablets in total in most of the cases. The serum concentration of Ig-E and peripheral eosinophils(/mm3) at the onset of the side effects were significantly higher than those before treatment. These results suggest that allergic mechanism rather than accumulating may concern the onset of side effects. Since in cases without the side effects the peripheral eosinophils at 3 to 4 weeks after administration were significantly higher than those before treatment and 19 of 51 (38.0%) cases without side effects had a high concentration of Ig-E of more than 500 u/ml, it is suggested that allergic mechanism may be triggered in most of Graves' patients who were administered methimazole or propylthiouracil. Thus, immunological disturbances in Graves' disease seems to be the cause of the side effects of antithyroid drugs, although there was no correlation between antithyroid autoantibodies and development of the side effects.

Recurrent agranulocytosis induced by two different antithyroid agents

A 45-year-old woman with thyrotoxicosis developed agranulocytosis after treatment with propylthiouracil. When the thyrotoxicosis recurred, accompanied by a severe psychotic reaction, administration of antithyroid medication was recommenced. The patient was given methimazole instead of propylthiouracil but, 10 weeks later, agranulocytosis again occurred. This is, to the best of our knowledge, the first report of a case in which agranulocytosis followed treatment with both propylthiouracil and methimazole in the same patient.

Causes of agranulocytosis in a hospital population: identification of dipyrone as an important causative agent

A population of patients with agranulocytosis admitted to a general hospital over a period of 12 yr was studied retrospectively in order to determine the causes of the disease. Of the 48 cases identified, 31 (65%) had drug-induced neutropenia, whereas 17 (35%) had chronic neutropenia unrelated to the use of drugs. Eight patients had an underlying hematological malignancy. Patients with agranulocytosis not induced by drugs more frequently had hepatomegaly, splenomegaly, enlarged lymph glands, or thrombocytopenia together with severe anemia. In contrast, drug-induced agranulocytosis was more severe, with a higher incidence of positive blood cultures, low cellularity of initial bone marrow aspirates, and a shorter duration of neutropenia. Dipyrone and methimazole were the drugs most commonly associated with agranulocytosis. Dipyrone was probably the causative agent in two of the seven drug-induced fatalities. In view of these findings, and those of several previous reports, it is proposed that the use of dipyrone in Israel be severely restricted or discontinued altogether.

Transient methimazole-induced bone marrow aplasia: in vitro evidence for a humoral mechanism of bone marrow suppression

A patient with methimazole-induced aplastic anemia is described. Despite severe pancytopenia and the complete disappearance of hemopoietic elements from the bone marrow, recovery of hemopoiesis has been observed within 14 days of discontinuing methimazole therapy. In vitro studies of CFU-C inhibition of peripheral mononuclear cells harvested in remission, were performed by incubation with autologous sera collected at earlier phases of the disease. These studies provide evidence in favor of a humoral, and most probably autoimmune mechanism as the cause of transient bone marrow aplasia.

Agranulocytosis associated with antithyroid drugs. Effects of patient age and drug dose

The records of all patients with antithyroid drug-related agranulocytosis at two Boston hospitals (Group 1, 14 patients), as well as the published case reports of 36 patients with this syndrome (Group 2) were reviewed. The clinical characteristics of these patients were then compared with those of 50 hyperthyroid patients who had taken antithyroid medication without untoward hematologic reactions (Group 3). The mean ages of patients in Group 1 and Group 2 were significantly greater than that of Group 3 (50.6 +/- 16 years versus 35.7 +/- 13.7 years, p less than 0.001; 46.3 +/- 18.7 years versus 35.7 +/-- 13.7 years, p less than 0.02). By chi-square analysis, the relative risk of developing agranulocytosis in patients over age 40 was 6.4 times that among younger patients (p less than 0.001). The mean doses of methimazole in Group 1 and Group 2 were significantly higher than that in Group 3 (43.8 +/- 9.9 mg/d versus 29.5 +/- 10.4 mg/d, p less than 0.001; 40.7 +/- 15.7 mg/d versus 29.5 +/- 10.4 mg/d, p less than 0.02), with and 8.6-fold increased risk of agranulocytosis with doses greater than 40 mg/d (p less than 0.01). In contrast, the mean doses of propylthiouracil did not differ among the three groups. These data suggest that antithyroid drugs should be administered cautiously to patients over age 40. Because no cases of agranulocytosis were seen with methimazole doses less than 30 mg/d, low-dose methimazole therapy may be safer than high-dose therapy or treatment with conventional doses of propylthiouracil.

Tectorial and basal membranes in experimental hypothyroidism

The aim of the study was to trace subtle changes in the membranous labyrinth after experimental hypothyroidism that, at least in part, could explain how a reversed hearing impairment can occur, as is often clinically encountered in hypothyroid patients after thyroid substitution therapy. Adult Sprague-Dawley rats were made hypothyroid during six weeks by the use of methimazole in their drinking water. Their inner ears were investigated morphologically at the end of this period. The tectorial membrane is the first structure of the inner ear to show morphologic changes in hypothyroidism. Changes in the normal position and structure constantly were found. A thickening of the basilar membrane was indicated in many, but not all, specimens and in some control animals and may be coincidental. The initial morphologic changes are likely to be reversible after substitution therapy.

[The adverse effects of thioureylene antithyroid drugs (author's transl)]

The aims of the present study were to investigate the incidence of adverse effects of thioureylene antithyroid drugs and to see if there were any factors related to the development of the adverse effects. Methimazole or propylthiouracil was administered to 151 patients with Graves disease; 76 untreated cases and 75 treated cases. The overall incidence was 22.4% among the 76 untreated cases. The incidences were 26.7% (13/45 cases) for methimazole and 16.1% (5/31 cases) for propylthiouracil, respectively, which were significantly higher than those previously reported. Fourteen out of 17 cases with the adverse effects were given the other thioureylene. The successive incidence of the adverse effects was 28.6% (4 cases), which was not significantly different from that under the drug of first choice. The result suggests that methimazole and propylthiouracil may not have cross-reaction each other. On the other hand, antinuclear antibody and anti-DNA antibody became positive in 2 out of the 4 cases. It would be a significant phenomenon, since antinuclear antibody was positive in only 3% of cases before the drug treatment. Thus, an immunological mechanism seemed to be involved in the problems, although there was no correlation between antithyroid autoantibodies and the development of the adverse effects. The adverse effects were observed within 2 months of administration of less than 250 tablets in total in most of the cases. The results imply that allergic mechanism rather than accumulating or toxic effect may concern the development of adverse effects of the thioureylenes.

[Reversible loss of taste as a side effect in thiamazole therapy]

In thyreostatic treatment the loss of taste combined with discreetly increasing hepatic enzymes has been observed as a toxic effect of thiamazole in a female patient. Sense and hepatic enzymes normalized rapidly after discontinuing use of thiamazole.

Lupus-like syndrome--a rare complication in thionamide treatment for Graves' disease

A patient with Graves' disease who experienced various allergic reactions to both PTU and MMI is reported. She developed fever, skin rash, lymphadenopathy, liver damage and moderate leukopenia during PTU administration. Furthermore, she developed an MMI-induced lupus-like syndrome characterized by generalized lymphadenopathy, migrating, polyarthritis and myalgia, and results of tests for anti-DNA antibody and anti-nuclear antibody, and LE were positive. All these abnormalities reverted to normal upon discontinuation of medication after subtotal thyroidectomy.

Familial thioamide-induced lupus syndrome in thyrotoxicosis

We describe 2 relatives both with thyrotoxicosis who developed a lupus-like syndrome after treatment with thioamide derivatives, methimazole (father) and propylthiouracil (son). The lupus syndrome consisted of joint pains, skin rash, and positive antinuclear antibodies (son), all of which resolved after discontinuation of the antithyroid medications. Both patients were identical at the HLA-DR locus suggesting adverse reactions to thioamides may be controlled by immune response genes. The clinician should be cautious about treating other family members when 1 member has had a drug-induced lupus syndrome. This is especially true if the disease in question is a known familial illness such as thyrotoxicosis.

The effect of rapeseed meal and methimazole on levels of plasma hormones in growing broiler cockerels

The effects of feeding a heat treated rapeseed meal, which has goitrogenic properties, on the concentrations of plasma pituitary and thyroid gland hormones was investigated in broiler cockerels of between 3 and 10 weeks of age. For purposes of comparison, two other groups were included in the study; one was fed the goitrogen, methimazole, and the other a normal control diet. The hormones measured were thyroxine (T4), triiodothyronine (T3), growth hormone (GH), prolactin, and luteinizing hormone (LH). In birds fed methimazole the thyroid glands were greatly enlarged, the concentrations of plasma T4 and T3 were depressed and the concentrations of growth hormone, prolactin, and LH were elevated. The high level of plasma LH in the birds fed methimazole was not due to the absence of sufficient concentrations of plasma testosterone to exert a negative feedback effect. Although the inclusion of rapeseed meal in the diet caused the thyroid glands to enlarge, the concentrations of all the hormones studied, with the exception of T3, were similar to those in the control birds. However, there was a tendency, which was more pronounced in birds of between 3 and 5 weeks of age, for rapeseed meal to depress the concentrations of plasma T4, GH, and LH and to increase the concentration of plasma prolactin. The most significant observation was that between 3 and 5 weeks of age the inclusion of rapeseed meal in the diet significantly (P less than .001) depressed the concentration of plasma T3.

Pseudothyrotoxic myopathy: a complication of thionamide therapy in hyperthyroidism

A hyperthyroid patient treated with methimazole for three weeks developed proximal muscle weakness, myalgia, arthralgia, and fever, and thyrotoxic myopathy was diagnosed. The signs and symptoms spontaneously abated when antithyroid medication was discontinued. This case identified a complication of thionamide treatment mimicking thyrotoxic myopathy and points to the therapeutic necessity of making such a differentiation.

The treatment of benign thyroid disease

The treatment of benign forms of thyroid disease is reviewed. Endemic goiter is a public health problem preventable by the addition of iodine to the food or water supply. Endemic and familial goiters are treated with replacement doses of I-thyroxine, as are sporadic colloid goiters and goiters resulting from chronic thyroiditis. Hyperfunctioning autionomous nodules without thyrotoxicosis and cystic nodules require no specific therapy. Prophylaxis against diffuse or nodular goiter after radiation to the head or neck for therapeutic purposes with thyroxine replacement therapy is debatable. All forms of hypothyroidism, including incipient types, require replacement thyroxine therapy, but this should be undertaken cautiously in older patients and in those with evidence of ischemic myocardial disease. Myxedema coma requires vigorous treatment and detailed supervision because of dismal mortality rates. Iodine 131 is the treatment of choice in diffuse toxic goiter, but alternative forms.

Nephrotic syndrome associated with methimazole therapy

Thionamide drugs are widely used in the management of hyperthyroidism and are infrequently associated with adverse reactions. We report the development of the nephrotic syndrome during methimazole (Tapazole) therapy in a young man with Graves' disease. His proteinuria remitted promptly with discontinuance of the drug, and renal histologic features bore a striking resemblance to the toxic nephrosis induced in animals by the aminonucleoside of puromycin. In view of the histologic similarities, we propose that methimazole acted as a direct glomerular toxin, inducing the nephrotic syndrome in this patient.

Reemergence of thyroidectomy as treatment for Graves' disease

Hyperthyroidism of Graves' disease may be treated very effectively by antithyroid pills, such as PTU and Tapazole, by radioactive iodine therapy, and by subtotal thyroidectomy. Each form of therapy has advantages and disadvantages, and thus treatment should be individualized. While therapy with radioactive iodine would appear to be ideal since it does not require an operation and is less expensive than surgical management, it suffers from a high rate of progressive hypothyroidism and from the fact that the time until a euthyroid state is obtained is often prolonged. In addition, the long-term carcinogenic risk of the therapy for thyroid neoplasia has never been completely defined since the data most often quoted have a mean follow-up time of only eight years. Furthermore, new "low-dose" radioiodine regimens may be more dangerous in this regard. Subtotal thyroidectomy, while not totally without complications, remains a rapid, safe, and effective treatment for Graves' disease. The careful use of propranolol has facilitated the preparation of some patients and has lessened the risk of operation. Thyroidectomy should remain the treatment of choice for young adults with this disease.

Drug-induced immunological neutropenia

Antineutrophil antibody capable of opsonising normal neutrophils was detected in the sera of 16 neutropenic patients receiving various drugs. A single drug was involved in 10 cases, multiple medication in 6. 4 patients received semisynthetic penicillins, 8 some form of antimicrobial, and 2 antithyroid agents. Neutrophil counts rose, and antineutrophil antibody activity declined or disappeared, after drug therapy was stopped. Opsonisation related to the semisynthetic penicillins was independent of complement but dependent on drug concentration. Complement-dependent opsonic activity was demonstrated in 2 patients (1 receiving methimazole and 1 receiving multiple medication) and in the patient receiving methimazole this activity was shown to reside in the IgM serum-fraction. In another patient receiving multiple drugs, a complement-independent IgG antibody was demonstrated.