Thyrotoxic, hypokalaemic periodic paralysis: Polynesians, an ethnic group at risk

Thyrotoxic Periodic Paralysis in a Samoan Male With Metabolic Acidosis: A Case Report and Review of the Literature

Thyrotoxic periodic paralysis (TPP) is a rare disorder characterized by muscle paralysis, thyrotoxicosis, and hypokalemia. It commonly manifests as paralysis of both proximal and distal upper and lower limbs, and if left untreated, may progress to respiratory failure or cardiac arrhythmias. It is most common in Asian males and is frequently precipitated by strenuous exercise, high carbohydrate diet, stress, corticosteroid therapy, or alcohol. Early diagnosis of TPP is crucial as the condition may be reversible with oral or IV potassium replacement therapy, and management of the underlying hyperthyroidism. We describe a Samoan man in his 30s who presented with acute onset lower extremity paralysis. Laboratory investigations revealed low serum potassium of 2.2 mEq/L (reference range 3.5-5.0 mEq/L) and thyrotoxicosis with a low (thyroid stimulating hormone (TSH) of <0.07 uIU/mL (reference range 0.27-4.20 uIU/mL) and an elevated free T4 of 5.4 ng/dL (reference range 0.9-2.1 ng/dL). He was treated with both oral and IV potassium chloride as well as propranolol and regained full strength in his extremities. While rare, TPP is a reversible complication of thyrotoxicosis and a high index of suspicion in clinical practice is essential to prevent adverse outcomes.

Unique Presentation of Thyrotoxic Periodic Paralysis With Urticarial Dermographia

Thyrotoxic periodic paralysis (TPP) is an acute complication of hyperthyroidism. Thyrotoxic periodic paralysis is treatable, and the management consists of potassium correction, beta-blockers, and antithyroid drug (ATD) therapy. While TPP is well described in the literature, we describe a case of TPP with urticarial dermographia (UD) that resolved with a short course of antihistamines while continuing ATD therapy. To the best of our knowledge, this is the first reported case of UD after methimazole (MMI) therapy in a TPP patient. A 25-year-old Cambodian active duty male with no significant past medical history presented to the emergency department with acute loss of lower extremity muscle tone with hypokalemia in the setting of previously undiagnosed Graves' disease (GD). He was started on MMI but within 2 weeks developed a rash consistent with UD. This was successfully treated with a second-generation antihistamine while continuing his MMI. Thyrotoxic periodic paralysis is primarily treated by controlling the underlying thyroid disease causing paralysis. Methimazole is commonly chosen as a treatment due to its rapid efficacy and long duration of action. However, adverse effects like UD can occur. Current recommendations are that minor cutaneous reactions can be treated with antihistamines for the management of Graves' disease. However, this case and others show that even moderate reactions can be managed in this manner. In a patient with TPP with UD after treatment with MMI, it is reasonable to attempt a trial of antihistamine before changing to another ATD.

Thyrotoxic Periodic Paralysis: An Under-Recognized Cause of Paralysis in Young Hispanic Men

BACKGROUND

Patients presenting to the emergency department with paralysis can have a wide differential diagnosis. Thyrotoxic periodic paralysis (TPP) is a rare disorder causing transient flaccid paralysis in the setting of thyrotoxicosis and hypokalemia. It has been reported in Asian male populations predominantly, and the diagnosis is rarely considered in non-Asian populations. Recent research has identified cases in patients with diverse ethnic backgrounds, although epidemiologic data from the United States are very limited.

OBJECTIVE

Our aim was to report our experience with TPP at a tertiary care center in the United States.

METHODS

A retrospective chart review was conducted between January 2006 and February 2022 to identify cases of TPP and determine their demographic and clinical characteristics. Prevalence of TPP was estimated using the institutional hyperthyroidism registry.

RESULTS

Thirty-three patients with TPP were identified. All of the patients were male; median age was 28 years, and 85% were Hispanic. All patients had hypokalemia at presentation and 23% had rebound hyperkalemia after treatment. Prevalence of TPP in our population of patients with hyperthyroidism was approximately 0.5%.

CONCLUSIONS

Young Hispanic men presenting with paralysis should be evaluated for TPP, as the prevalence in this population may be higher than estimated previously. Management of TPP involves treatment of underlying hyperthyroidism and cautious potassium repletion, with an initial dose of no more than 60 mEq/L of potassium chloride to avoid rebound hyperkalemia.

Prolonged Exercise Test in Patients With History of Thyrotoxicosis

PURPOSE

Thyrotoxic periodic paralysis is characterized by recurrent episodes of reversible, severe proximal muscle weakness associated with hypokalemia and hyperthyroidism. Prolonged exercise test is an easy, noninvasive method of demonstrating abnormal muscle membrane excitability in periodic paralyses. Although abnormal in thyrotoxic periodic paralysis patients, the effects thyroid hormone levels in non-thyrotoxic periodic paralysis thyrotoxicosis patients have not been well studied. The study aims to evaluate thyrotoxicosis patients (regardless of thyrotoxic periodic paralysis history) with prolonged exercise test and correlate it with their thyroid status.

METHODS

This is a prospective, cross-sectional study of consecutive thyrotoxicosis patients seen at the endocrine clinic of a tertiary medical center. Thyroid status was determined biochemically before prolonged exercise test. Compound muscle action potential (CMAP) amplitudes postexercise were compared against pre-exercise amplitudes and recorded as percentage of mean baseline CMAP amplitude. Comparisons of time-dependent postexercise CMAP amplitudes and mean CMAP amplitude decrement were made between hyperthyroid and nonhyperthyroid groups.

RESULTS

Seventy-four patients were recruited, 23 (31%) men, 30 (41%) Chinese, and the mean age was 48.5 ± 16.8 years. Of 74 patients, 32 (43%) were hyperthyroid and 42 (57%) were nonhyperthyroid viz. euthyroid and hypothyroid. Time-dependent CMAP amplitudes from 10 to 45 minutes after exercise were significantly lower in hyperthyroid patients compared with nonhyperthyroid patients (P < 0.01). Mean CMAP amplitude decrement postexercise was significantly greater in hyperthyroid than nonhyperthyroid patients (23.4% ± 11.4% vs. 17.3% ± 10.5%; P = 0.02).

CONCLUSIONS

Compound muscle action potential amplitude declines on prolonged exercise test were significantly greater in hyperthyroid patients compared with nonhyperthyroid patients. Muscle membrane excitability is highly influenced by thyroid hormone level. Thyrotoxic periodic paralysis occurs from increased levels of thyroid hormone activity in susceptible patients.

Thyrotoxic Periodic Paralysis: A Case Report and Literature Review

Thyrotoxic periodic paralysis (TPP) is a rare presentation of thyrotoxicosis most commonly associated with Graves' disease. It is rare in Caucasians, but it affects approximately 2% of Asians (occurring in those of Chinese, Japanese, Vietnamese, Filipino, and Korean descent) with thyrotoxicosis of any cause. Typical thyrotoxic features may be absent despite biochemical thyrotoxicosis. Hypokalemia and muscle paralysis are the result of an acute intracellular shift of potassium and not due to total body potassium deficiency. TPP is a self-limiting condition that is easily corrected by treatment of the thyrotoxicosis. We present a case of a Filipino man, aged 47 years, who presented to the emergency department with acute bilateral lower extremity weakness and hypokalemia who was subsequently diagnosed with TPP due to Graves' disease.

Thyrotoxic Hypokalemic Periodic Paralysis: A Success Story of a Diagnostic Challenge

Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare but life-threatening complication of hyperthyroidism seen predominantly in males. It is generally characterized by hypokalemia and skeletal muscle paralysis requiring intensive care admission. Hypokalemia occurs due to the massive intracellular shift of potassium because of the hyperactivity of the sodium-potassium adenosine triphosphates pump (Na⁺ K⁺ ATPase). Its differential diagnosis from the other common causes of hypokalemic paralysis is essential to provide targeted therapy. We present a rare case of THPP in a female patient with no prior history of thyroid disease. THPP in this patient was precipitated by trauma and emotional stress, which served as a diagnostic challenge. Both hypokalemia and elevated levels of T3 and T4 are important diagnostic features during the acute episode. Treatment of THPP includes nonselective beta-blockade, which prevents the shift of intracellular potassium, and potassium replacement. THPP is curable once a euthyroid state is achieved.

Thyrotoxic periodic paralysis: case report and review of the literature

Introduction

Thyrotoxic periodic paralysis (TPP) is a rare and potentially lethal complication of hyperthyroidism. It is characterized by sudden onset paralysis associated with hypokalemia. Management includes prompt normalization of potassium, which results in resolution of the paralysis. Definitive treatment of hyperthyroidism resolves TPP completely.

Case presentation

A 23-year-old African American male patient presented to the emergency room at the University of Mississippi Medical Center, USA in November 2016 with sudden onset quadriplegia. He also endorsed a history of weight loss, palpitations, heat intolerance and tremors. The patient reported similar episodes of quadriplegia in the past, which were associated with hypokalemia and resolved with normalization of potassium levels. Physical examination was significant for exophthalmos, smooth goiter with bruit consistent with the diagnosis of Graves’ disease. Laboratory assessment showed severe hypokalemia, hypomagnesemia, suppressed thyroid stimulating hormone (TSH) and high free thyroxine (T4). Urine potassium creatinine ratio was less than one, indicating transcellular shift as the cause of hypokalemia. After normalization of potassium and magnesium, the paralysis resolved in 12 hours. He was started on methimazole. On follow up, the patient was clinically and biochemically euthyroid with no further episodes of paralysis.

Take-away lesson

TPP is a rare and reversible cause of paralysis. Physicians need to be aware of the diagnostic and treatment modalities as delayed recognition in treatment could result in potential harm or unnecessary interventions.

Profound Hypokalaemia Resulting in Maternal Cardiac Arrest: A Catastrophic Complication of Hyperemesis Gravidarum?

We present a case of a 39-year-old G8P6 Pacific Islander woman who at 15+5 weeks' gestation had an out-of-hospital cardiac arrest secondary to profound hypokalaemia which was associated with severe hyperemesis gravidarum (HG). Her clinical course after arrest was complicated by a second 5-minute cardiac arrest in the Intensive Care Unit (ICU) (pre-arrest potassium 1.8), anuric renal failure requiring dialysis, ischaemic hepatitis, and encephalopathy and unfortunately fetal demise and a spontaneous miscarriage on day 2 of admission. Despite these complications, she was discharged home 4 weeks later with a full recovery. Following a plethora of inpatient and outpatient investigations, the cause of her cardiac arrest was determined to be profound hypokalaemia. The hypokalaemia was presumed second to a perfect storm of HG with subsequent nutritional deficiencies causing electrolyte wasting, extracellular fluid (ECF) volume reduction, and activation of the renin-angiotensin-aldosterone axis (RAAS). This combined with the physiological changes that promote potassium wasting in pregnancy including volume expansion, increased renal blood flow, increased glomerular filtration rate, and increase in cortisol contributed to the patient having a profoundly low total body potassium level. This diagnosis is further strengthened by the fact that her pre- and post-pregnancy potassium levels were within normal limits in the absence of supplementary potassium. This case highlights the potentially life-threatening electrolyte imbalances that can occur with HG and the importance of recognising the disease, comprehensive electrolyte monitoring, and aggressive management in pregnancy.

Etiological Search and Epidemiological Profile in Patients Presenting with Hypokalemic Paresis: An Observational Study

INTRODUCTION

Hypokalemia is associated with increased morbidity and at times mortality. "Hypokalemic paralysis", particularly if recurrent, has often been considered synonymous with "hypokalemic periodic paralysis (HPP)"; however, diseases such as Gitelman syndrome (GS), Bartter syndrome (BS), and renal tubular acidosis (RTA) can have identical presentation. We have tried to explore the etiological spectrum along with epidemiological and certain clinical, biochemical, and electrophysiological features in patients with hypokalemic paralysis.

MATERIALS AND METHODS

In this observational study, 200 appropriate patients with hypokalemic paralysis (serum K⁺ <3.5 mmol/L) were evaluated for transcellular shift, extra-renal or renal loss of K⁺ as the underlying etiology of hypokalemia. We took urinary potassium >25 mmol/day as the cutoff for inappropriate renal loss of potassium in presence of hypokalemia. Serum and urinary osmolality along with arterial blood gas analysis were performed in all patients with renal loss of potassium. Serum and urinary sodium, potassium, calcium, magnesium, chloride, and creatinine were measured in normotensive patients with metabolic alkalosis. Hypertensive patients were evaluated with plasma aldosterone and renin activity.

RESULTS

Probable GS topped the list involving 28% individuals of the entire cohort while probable BS, distal RTA, and HPP were diagnosed in 20%, 22%, and 19% cases, respectively. Rural tribal population (61%) and age group of 30-40 years suffered the most (48%) with concentration of cases in hot and humid summer months.

CONCLUSIONS

We suggest that patients with hypokalemic paresis should be evaluated thoroughly to unmask the underlying etiology that may have a different therapeutic and prognostic connotations and not to use the term "periodic" in cases of recurrent hypokalemic paralysis.

Hickam's dictum: Myasthenia Gravis presenting concurrently with Graves' disease

We present two patients with Graves' disease and concurrent myasthenia gravis. The impact of the dual diagnosis on the clinical course and the potential for a delayed diagnosis of myasthenia gravis is discussed. Patient 1, a 28-year-old man was diagnosed with Graves' disease following his second respiratory arrest. His history was strongly suggestive of a second pathology. Patient 2, a 66-year-old Cantonese woman with established Graves' disease presented with thionamide-related neutropaenia. Examination revealed bilateral ptosis and right lateral rectus palsy. Both patients had thyrotoxicosis secondary to Graves' disease with concurrent myasthenia gravis. Although neuromuscular weakness is common in Graves' disease, coexisting myasthenia gravis (MG) is rare and can cause profound morbidity. Ocular signs in both diseases may cause diagnostic confusion although ptosis suggests coexisting MG. In both cases, the thyrotoxicosis delayed the diagnosis of MG.

Ethnic disparities in thyroid surgery outcomes in New Zealand

BACKGROUND

Although thyroid disease is known to have significant ethnic variability, ethnic disparities in outcomes of thyroid surgery have been poorly studied.

METHOD

Retrospective review of 716 consecutive thyroid operations at Counties Manukau Health, a public health provider in New Zealand, from January 2002 to August 2013.

RESULTS

Compared with Europeans, Māori and Pacific Islanders have longer operation times (P < 0.001) and heavier thyroid glands (P < 0.001). Polynesians also had higher risk of post-operative haemorrhage compared with non-Polynesians (P = 0.016). They also have higher body mass index, American Society of Anesthesiologists scores and rates of smoking. There were no differences in length of inpatient stay and readmission rates.

CONCLUSIONS

There are significant ethnic differences in certain outcomes of thyroid surgery. Part of this may be explained by higher co-morbid characteristics.

Case of thyrotoxic periodic paralysis in a caucasian male and review of literature

Objective. Thyrotoxic periodic paralysis (TPP), a known condition in Asian men, is becoming increasingly common in men from Western countries. Since suspicion for TPP as a differential in diagnosis is of utmost importance to avoid overcorrection of hypokalemia and other complications, we are reporting a case of TPP in a 25-year-old Caucasian male. Methods. The patient presented with intermittent lower extremity weakness after consumption of a large high-carbohydrate meal. Clinical examination revealed diffusely enlarged thyroid gland, no muscle power in lower extremities, tremors, and brisk deep tendon reflexes. Results. Clinical and laboratory findings were consistent with Graves' disease and the patient had hypokalemia. The patient responded to potassium repletion and was treated with propylthiouracil and propranolol. After treatment with radioactive iodine, the patient developed postablative hypothyroidism for which he was treated with levothyroxine. Conclusion. Since this condition is overlooked by physicians in Western countries, we present a case of TPP in a Caucasian male thus showing the importance of consideration of TPP in Caucasians despite its rare occurrence and the need for prompt diagnosis to avoid the danger of hyperkalemia in management of the paralytic attack in TPP patients.

Thyrotoxic periodic paralysis in Chinese patients: milder thyrotoxicosis yet lower dose of (131)I should be avoided

PURPOSE

Thyrotoxic periodic paralysis (TPP) is a complication of thyrotoxicosis mainly observed in male Asian patients. It was proposed that patients with TPP tend to have lower thyroid hormone levels. We aimed to prove this observation and to assess whether a lower I dose is feasible for prompt control of TPP.

METHODS

A total of 123 male TPP patients were enrolled in this study in a 7-year period. Baseline characteristics were compared with 70 thyrotoxic patients without periodic paralysis (nTPP). Different I doses were given to 90 TPP patients with a median follow-up of 11 months, and the outcome was evaluated.

RESULTS

The serum thyroid hormone levels, including total T3 and T4, and free T3 and T4, in TPP patients were slightly less elevated compared with those in nTPP patients. Patients who received lower radioactivity of I had an unsatisfactory overall remission rate of 28.6%. Longer time to remission (P = 0.004; hazard ratio, 1.846; 95% confidence interval, 1.216-2.798) was also observed in patients with lower dose.

CONCLUSIONS

The serum thyroid hormone levels of TPP patients are lower than those of nTPP patients. Median/high dose of I is necessary to achieve rapid control of thyrotoxicosis.

Thyrotoxic hypokalemic periodic paralysis as the presenting symptom of silent thyroiditis

Silent thyroiditis is a rare cause of thyrotoxic periodic paralysis. The objective was to present a case of silent thyroiditis presenting as periodic paralysis. A 23-year-old man presented with recurrent acute flaccid predominantly proximal weakness of all four limbs. He had a similar episode 3 weeks back. On examination he was found to have hypokalemia secondary to thyrotoxicosis. Clinically there were no features of thyrotoxicosis or thyroiditis. He was initially treated with intravenous and later oral potassium supplementation and propranolol. At 8 weeks of follow-up his thyroid profile became normal and his propranolol was stopped. He had no further recurrence of paralysis. He was diagnosed as a case silent thyroiditis presenting as thyrotoxic periodic paralysis. In cases of recurrent or acute flaccid muscle paralysis, it is important to suspect thyrotoxicosis, even if asymptomatic. Definitive treatment of thyrotoxicosis prevents recurrence.

Clinical and biochemical spectrum of hypokalemic paralysis in North: East India

Background:

Acute hypokalemic paralysis, characterized by acute flaccid paralysis is primarily a calcium channelopathy, but secondary causes like renal tubular acidosis (RTA), thyrotoxic periodic paralysis (TPP), primary hyperaldosteronism, Gitelman’s syndrome are also frequent.

Objective:

To study the etiology, varied presentations, and outcome after therapy of patients with hypokalemic paralysis.

Materials And Methods:

All patients who presented with acute flaccid paralysis with hypokalemia from October 2009 to September 2011 were included in the study. A detailed physical examination and laboratory tests including serum electrolytes, serum creatine phosphokinase (CPK), urine analysis, arterial blood gas analysis, thyroid hormones estimation, and electrocardiogram were carried out. Patients were further investigated for any secondary causes and treated with potassium supplementation.

Result:

The study included 56 patients aged 15-92 years (mean 36.76 ± 13.72), including 15 female patients. Twenty-four patients had hypokalemic paralysis due to secondary cause, which included 4 with distal RTA, 4 with Gitelman syndrome, 3 with TPP, 2 each with hypothyroidism, gastroenteritis, and Liddle’s syndrome, 1 primary hyperaldosteronism, 3 with alcoholism, and 1 with dengue fever. Two female patients were antinuclear antibody-positive. Eleven patient had atypical presentation (neck muscle weakness in 4, bladder involvement in 3, 1 each with finger drop and foot drop, tetany in 1, and calf hypertrophy in 1), and 2 patient had respiratory paralysis. Five patients had positive family history of similar illness. All patients improved dramatically with potassium supplementation.

Conclusion:

A high percentage (42.9%) of secondary cause for hypokalemic paralysis warrants that the underlying cause must be adequately addressed to prevent the persistence or recurrence of paralysis.

Thyrotoxic periodic paralysis: clinical and molecular aspects

Thyrotoxic periodic paralysis (TPP) is a rare complication of hyperthyroidism that most often affects young East Asian males but increasingly also in other ethnic groups. The typical presentation is acute attacks varying from mild weakness to total paralysis starting at night or in the early morning a few hours after a heavy meal, alcohol abuse or strenuous exercise with complete recovery within 72 h. Signs and symptoms of hyperthyroidism may not be obvious. The hallmark is hypokalemia from increased cellular sodium/potassium-ATPase pump activity with transport of potassium from the extracellular to the intracellular space in combination with reduced potassium output. Recently, KCNJ18 gene mutations which alter the function of an inwardly rectifying potassium channel named Kir2.6 have been detected in 0-33 % of cases. Hence, the pathophysiology in TPP includes a genetic predisposition, thyrotoxicosis and environmental influences and the relative impact from each of these factors may vary. The initial treatment, which is potassium supplementation, should be given with caution due to a high risk of hyperkalemia. Propranolol is an alternative first-line therapeutic option based on the assumption that hyperadrenergic activity is involved in the pathogenesis. If thyroid function tests are unobtainable in the acute situation the diagnosis is supported by the findings of hypokalemia, low spot urine potassium excretion, hypophosphatemia with hypophosphaturia, high spot urine calcium/phosphate ratio, and electrocardiographic abnormalities as tachycardia, atrial fibrillation, high QRS voltage, and atrioventricular block. Definitive treatment is cure of the hyperthyroidism. The underlying mechanisms of TPP remain, however, incompletely understood awaiting further studies.

Thyrotoxic periodic paralysis

This article aims at highlighting the importance of suspecting thyrotoxicosis in cases of recurrent periodic flaccid paralysis; especially in Asian men to facilitate early diagnosis of the former condition. A case report of a 28 year old male patient with recurrent periodic flaccid paralysis has been presented. Hypokalemia secondary to thyrotoxicosis was diagnosed as the cause of the paralysis. The patient was given oral potassium intervention over 24 hours. The patient showed complete recovery after the medical intervention and was discharged after 24 hours with no residual paralysis. Thyrotoxic periodic paralysis (TPP) is a complication of thyrotoxicosis, more common amongst males in Asia. It presents as acute flaccid paralysis in a case of hyperthyroidism with associated hypokalemia. The features of thyrotoxicosis may be subtle or absent. Thus, in cases of recurrent or acute flaccid muscle paralysis, it is important to consider thyrotoxicosis as one of the possible causes, and take measures accordingly.

Novel etiopathophysiological aspects of thyrotoxic periodic paralysis

Thyrotoxicosis can lead to thyrotoxic periodic paralysis (TPP), an endocrine channelopathy, and is the most common cause of acquired periodic paralysis. Typically, paralytic attacks cease when hyperthyroidism is abolished, and recur if hyperthyroidism returns. TPP is often underdiagnosed, as it has diverse periodicity, duration and intensity. The age at which patients develop TPP closely follows the age at which thyrotoxicosis occurs. All ethnicities can be affected, but TPP is most prevalent in people of Asian and, secondly, Latin American descent. TPP is characterized by hypokalemia, suppressed TSH levels and increased levels of thyroid hormones. Nonselective β adrenergic blockers, such as propranolol, are an efficient adjuvant to antithyroid drugs to prevent paralysis; however, an early and definitive treatment should always be pursued. Evidence indicates that TPP results from the combination of genetic susceptibility, thyrotoxicosis and environmental factors (such as a high-carbohydrate diet). We believe that excess T(3) modifies the insulin sensitivity of skeletal muscle and pancreatic β cells and thus alters potassium homeostasis, but only leads to a depolarization-induced acute loss of muscle excitability in patients with inherited ion channel mutations. An integrated etiopathophysiological model is proposed based on molecular findings and knowledge gained from long-term follow-up of patients with TPP.

Analytic review: thyrotoxic periodic paralysis: a review

Thyrotoxic periodic paralysis (TPP) is an unusual complication of hyperthyroidism that frequently presents in a dramatic fashion, necessitating treatment in an emergency department or admission to an intensive care unit. Thyrotoxic periodic paralysis is characterized by transient, recurrent episodes of flaccid muscle paralysis affecting proximal more severely than distal muscles. Thyrotoxic periodic paralysis is most commonly a complication of Graves' disease in Asian males, although in recent decades, an increasing number of patients from all racial and ethnic backgrounds have been reported. Thyrotoxic periodic paralysis has a higher predilection for men than women despite the fact that thyroid disease is more frequently diagnosed in women. The presence of both hypokalemia and elevated levels of triiodothyronine (T3) and thyroxine (T4) are important diagnostic features during the acute episode. Treatment of TPP involves 2 steps, immediate action to reverse the paralysis followed by measures to prevent future attacks by restoration of a euthyroid state. Although the mainstay of treating an acute attack of TPP is correction of hypokalemia to avoid fatal cardiac arrhythmias and reverse muscle weakness, it must be appreciated by treating physicians that patients with TPP do not have a total body deficiency of potassium. Close attention must be given to potassium replacement as overly aggressive treatment can result in hyperkalemia. Correction of hypokalemia and the underlying thyrotoxic state usually results in amelioration of the acute attack. This review summarizes the epidemiology, clinical manifestations, pathogenesis, diagnosis, and treatment of TPP.

Thyrotoxic hypokalemic periodic paralysis: a life-threatening syndrome

Hypokalemic periodic paralysis is a rare life-threatening syndrome, potentially reversible when detected at an early stage. Hypokalemia may also occur in other conditions characterized by muscle weakness. Acute myopathy associated with thyrotoxicosis has been described in Asian populations, although it seldom affects Caucasians or African-Americans. It can be difficult to recognize in western populations. Acute recurrent episodes of flaccid paralysis, symmetrically affecting the proximal muscles of the lower limbs, either following strenuous physical activity or carbohydrate overindulgence, is the usual presentation. Hypokalemia seems to result from transcellular shifts of potassium rather than losses. A case of thyrotoxic hypokalemic periodic paralysis occurring in a young Caucasian male diagnosed with Graves' disease is reported.

Hypokalemic thyrotoxic periodic paralysis: clinical characteristics and predictors of recurrent paralytic attacks

BACKGROUND AND PURPOSE

To study the clinical characteristics of hypokalemic thyrotoxic periodic paralysis (hoTPP) and identify the predictors of recurrent paralytic attacks before achieving the euthyroid status.

METHODS

We retrospectively analyzed 45 hoTPP patients who were admitted during the 7-year study period.

RESULTS

A tendency towards male predominance was observed among the 45 patients (91.1%, 41/45). The mean onset age was 32.9 +/- 10.0 years (range: 16-54 years). No significant differences were observed in the onset age between male and female patients. Precipitating factors included rest/sleep at night, hot weather, upper respiratory tract infections (URIs), and excessive physical activities. Atypical weakness was observed in nine (20%, 9/45) patients. One patient initially diagnosed with sporadic periodic paralysis eventually developed hoTPP.

DISCUSSION

In provocative tests, hypokalemia was not a consistent finding during paralytic attacks. Before achieving the euthyroid status, the rate of recurrent attacks was as high as 62.2%, and peaked in the first 3 months after hoTPP was diagnosed. Patients with URIs exhibited a higher incidence of recurrent paralytic attacks than those without (odds ratio = 13.00; 95% confidence interval = 1.08-156.08; P = 0.04).