Hyperthyroidism

A 10-year analysis of thyrotoxic periodic paralysis in 135 patients: focus on symptomatology and precipitants

BACKGROUND

A comprehensive analysis has not been performed on patients with thyrotoxic periodic paralysis (TPP) characterized by acute hypokalemia and paralysis in the setting of thyrotoxicosis.

PURPOSE

The aim of this study was to analyze the detailed symptomatology of thyrotoxicosis and precipitating factors for the attack in a large cohort of TPP patients.

PATIENTS AND METHODS

A prospective observational study enrolled patients with TPP consecutively over 10 years at an academic medical center. Clinical features, including signs/symptoms of thyrotoxicosis and precipitating factors, were analyzed. The Wayne's index was used to assess the severity of thyrotoxicosis at presentation. Patients who agreed to receive an oral glucose-loading test after recovery were evaluated.

RESULTS

Among the 135 TPP patients (male:female, 130:5), 70% of paralytic attacks occurred in the morning, especially during the seasons of summer and fall. Two-thirds of patients did not have a known family or personal history of hyperthyroidism. Only 17% of TPP patients manifested overt signs/symptoms of thyrotoxicosis (Wayne's index >19). A clear precipitating factor, such as high carbohydrate load, acute upper respiratory tract infection, strenuous exercise, high-salt diet, or the use of steroids or bronchodilators, was identified in only 34% of TPP patients. A glucose load to stimulate insulin secretion induced acute hypokalemia (K(+)2.47±0.6 mmol/l) with reparalysis in only 18% (10/55) of TPP patients.

CONCLUSIONS

Most TPP patients have only subtle clinical signs/symptoms of thyrotoxicosis and only a small fraction has clear precipitating factors. In addition to the effects of hyperinsulinemia, other insulin-independent mechanisms may participate in the pathogenesis of TPP.

Clinical scoring scales in thyroidology: A compendium

This compendium brings together traditional as well as contemporary scoring and grading systems used for the screening and diagnosis of various thyroid diseases, dysfunctions, and complications. The article discusses scores used to help diagnose hypo-and hyperthyroidism, to grade and manage goiter and ophthalmopathy, and to assess the risk of thyroid malignancy.

Carcinoma in hyperfunctioning thyroid nodule in recurrent hyperthyroidism

A patient with an invasive thyroid carcinoma located within a hot thyroid nodule is reported. Only four similar cases have been described in the literature. It is emphasized that a hot thyroid nodule per se should not be used as an argument against the diagnosis of thyroid carcinoma.

The diagnosis of thyrotoxicosis

Thyrotoxicosis is a clinical syndrome due to excessive amounts of thyroid hormone in the circulation and tissues. Graves' disease, goitre and exophthalmos, is the commonest variety, but in some parts of the world thyrotoxicosis supervenes on the background of a long standing nodular goitre. Other varieties such as ectopic TSH syndromes are very rare.

The diagnostic sequence in practice starts with clinical suspicion and a decision can often be made on the symptoms and signs alone. It is, however, always advisable to confirm the presence or absence of thyrotoxicosis. There has been re-orientation in the simple test procedure used in this respect. Measurements such as serum TSH and serum TSH response to TRH and measurements of serum LATS levels are available only in a few centres and are not discussed in detail.

Tests based on the carriage of thyroid hormones in the blood are preferable to in vivo radionuclide studies, particularly when the patient is thought to be euthyroid. We advise a serum PB¹²⁷I and serum total thyroxine estimation in all patients. If the data are abnormal we add a serum T3 resin estimation to check whether the values are due, for example, to iodine contamination or altered binding.

We advise radionuclide studies in all doubtful cases and measurements such as the 4 hr or 24 hr ¹³¹I uptake and the 48 hr serum PB¹³¹I are very helpful. A thyroid uptake suppression test may be required if there is still doubt. In general those patients going for thyroidectomy or ¹³¹I therapy should have a scan performed. With improved technology much safer radionuclides, such as ¹²³I or ^99mTc, may be usable when thyrotoxicosis is suspected in children or during pregnancy.