Occurrence of hyperthyroidism in patients receiving thyroid hormone

Thyroid hormone misuse and abuse

Thyroid hormone (TH) plays an essential role in human physiology and maintenance of appropriate levels is important for good health. Unfortunately, there are instances in which TH is misused or abused. Such misuse may be intentional such as when individuals take thyroid hormone for unapproved indications like stimulation of weight loss or improved energy. There are instances where healthcare providers prescribe thyroid hormone for controversial or out of date uses and sometimes in supraphysiologic doses. Othertimes, unintentional exposure may occur through supplements or food that unknowingly contain TH. No matter the reason, exposure to exogenous forms of TH places the public at risk for potential adverse side effects.

Clinical features and pathogenesis of thyrotoxicosis in adult Melanesians in Papua New Guinea

OBJECTIVE

To investigate the cause of an apparent increase in the incidence of thyrotoxicosis in the Melanesian population of the coastal areas around Port Moresby, Papua New Guinea.

DESIGN

Consecutive patients attending the thyroid clinic at Port Moresby General Hospital were included in the study which collected clinical and immunogenetic data.

PATIENTS

One hundred and ninety-four patients with thyrotoxicosis were studied. The mean age was 31 years. The clinical features were typical for thyrotoxicosis apart from increased pigmentation, which occurred in the majority of patients and which reversed with treatment with antithyroid drugs and resolution of the thyrotoxicosis.

MEASUREMENTS

Antibodies to thyroid peroxidase, thyroglobulin and the thyrotropin receptor were present in 99%, 52% and 69% of patients, respectively, confirming that all cases were caused by autoimmune thyroid disease. Fine needle aspirations in 42 of 43 patients were consistent with Graves' disease.

CONCLUSIONS

The cause of this apparent sudden increase in Graves' disease in the coastal region around Port Moresby, an apparently iodine-replete area, remains unexplained.

Thyroxine suppression therapy in Graves' disease

A recent Japanese report of a novel 'block-and-replace' regime for Graves' hyperthyroidism in which thyroxine was continued alone after the combination therapy was stopped was associated with a negligible relapse rate of less than 2%. Such a finding has the potential to revolutionize the management of Graves' disease but a similarly large study from Scotland failed to confirm any benefit from the new treatment. Apart from obvious differences in race and dietary iodine there is no adequate explanation for the discrepant results. In all studies reporting a fall in thyrotropin (TSH) receptor antibodies (TRAb) and/or relapse rates following conventional or novel 'block-and-replace' regimes, serum TSH concentrations were often elevated in the control groups treated with antithyroid drugs alone. Theoretically, this could lead to continued expression of thyroid cell surface antigen, increased production of TRAb and an adverse effect on remission rates. This, however, fails to explain the extraordinary low remission rates of the original study from Japan and, in the meantime, there is no good reason to adopt the novel regime, at least in Caucasians.

An outbreak of thyrotoxicosis caused by the consumption of bovine thyroid gland in ground beef

We report an outbreak of thyrotoxicosis without true hyperthyroidism that occurred between April 1984 and August 1985 among residents of southwestern Minnesota and adjacent areas of South Dakota and Iowa. One hundred twenty-one cases were identified through surveillance of medical clinics, laboratories, hospitals, and physicians' offices. Investigation of the outbreak demonstrated an association between the occurrence of thyrotoxicosis and the consumption of ground beef prepared from neck trimmings processed by a single slaughtering plant (odds ratio, 19.0; P = 0.0001). The cause was confirmed by the findings of bovine thyroid tissue in samples of these trimmings and high concentrations of thyroid hormone in implicated samples of ground beef and the demonstration of prompt increases in serum thyroid hormone concentrations in volunteers who ate the implicated ground beef. Bovine thyroid tissue had been introduced into the neck trimmings inadvertently during the process of "gullet trimming," a procedure that harvests muscles from the bovine larynx. The outbreak resolved after this procedure was discontinued at the plant. The clinical features of the illness suggested the diagnosis of silent thyroiditis, and it is possible that sporadic cases--or even outbreaks--of thyrotoxicosis factitia caused by this mechanism may have occurred in the past but were not recognized.

Hyperthyroidism following hypothyroidism

Two patients are presented who developed autonomous thyrotoxicosis following a diagnosis of primary hypothyroidism. In one of these patients, antibodies to the TSH receptor were typical of Graves' disease when measured as thyrotropin binding inhibitor immunoglobulins (TBII) and as human thyroid adenylate cyclase stimulating (HTACS) activity, while a needle biopsy of the thyroid gland was consistent with lymphocytic thyroiditis. Twenty-one other reported cases of this unusual sequence found in the literature are reviewed. This occurrence is more common than is generally appreciated.

Graves' disease in pregnancy years after hypothyroidism with recurrent passive-transfer neonatal Graves' disease in offspring. Therapeutic considerations

Symptoms and signs of severe hypothyroidism developed in a young woman at age 15. These symptoms progressed for a year; at age 16, she was found to have a firm goiter, thyroid autoantibodies, very low serum thyroxine and high thyrotropin values, indicating autoimmune thyroiditis with hypothyroidism. She received L-thyroxine, 0.20 mg per day, and was well until age 24 when she became pregnant. In the first trimester, manifestations indicative of hyperthyroidism developed; these were only ultimately recognized immediately after delivery of a 32-week still-born goitrous baby. Despite the discontinuation of thyroxine therapy, the hyperthyroidism persisted and was confirmed as Graves' disease by elevated thyroxine, triiodothyronine, and radioactive iodine uptake values, a diffuse scanning result, and the presence of thyroid-stimulating antibody. The patient was treated with propylthiouracil and became pregnant while receiving that regimen. Later, several months after delivery, the patient was treated with radioactive iodine, ultimately became hypothyroid, and has been treated ever since with thyroxine. She became pregnant again and, because of the continuing high titers of thyroid-stimulating antibody, received propylthiouracil, 100 mg daily, commencing in the third trimester of pregnancy, to avoid probable fetal hyperthyroidism due to the transplacental transfer of thyroid-stimulating antibody. In each of the last two pregnancies, when the infants were born, they seemed normal (because of the transplacental effect of propylthiouracil), but passive-transfer neonatal hyperthyroidism developed in each within 10 days after delivery, ultimately requiring treatment by conventional means. This case illustrates the following points: (1) Hyperthyroidism occasionally develops years after hypothyroidism. (2) In young women, high titers of thyroid-stimulating antibody may produce fetal and neonatal passive-transfer hyperthyroidism even at a time when the mother herself is no longer hyperthyroid; transplacental treatment of the fetus by maternal propylthiouracil ingestion may thus be necessary during the last trimester, but only when there is a high degree of probability that the fetus is at risk. (3) Because the infants had been protected in utero by the placental transfer of propylthiouracil, neonatal hyperthyroidism did not develop until several days after delivery.(ABSTRACT TRUNCATED AT 400 WORDS)

Triiodothyronine thyrotoxicosis complicating primary hypothyroidism in a patient with autoimmune thyroiditis

It is increasingly recognized that autoimmune thyroiditis can have a multifaceted presentation. Documented triiodothyronine thyrotoxicosis developed in a patient with a six-year history of primary hypothyroidism that was left untreated. Serologic and cytologic evidence confirmed the thyroid dysfunction as being on an autoimmune basis. Chronic lymphocytic thyroiditis may be seen with hyperthyroidism, hypothyroidism, or euthyroidism, and in an individual patients, spontaneous progression from one metabolic state to another may occur.