Hypothyroidism Impairs Human Stem Cell-Derived Pancreatic Progenitor Cell Maturation in Mice

Pancreatic progenitors derived from human embryonic stem cells (hESCs) are a potential source of transplantable cells for treating diabetes and are currently being tested in clinical trials. Yet, how the milieu of pancreatic progenitor cells, including exposure to different factors after transplant, may influence their maturation remains unclear. Here, we examined the effect of thyroid dysregulation on the development of hESC-derived progenitor cells in vivo. Hypothyroidism was generated in SCID-beige mice using an iodine-deficient diet containing 0.15% propyl-2-thiouracil, and hyperthyroidism was generated by addition of L-thyroxine (T4) to drinking water. All mice received macroencapsulated hESC-derived progenitor cells, and thyroid dysfunction was maintained for the duration of the study ("chronic") or for 4 weeks posttransplant ("acute"). Acute hyperthyroidism did not affect graft function, but acute hypothyroidism transiently impaired human C-peptide secretion at 16 weeks posttransplant. Chronic hypothyroidism resulted in severely blunted basal human C-peptide secretion, impaired glucose-stimulated insulin secretion, and elevated plasma glucagon levels. Grafts from chronic hypothyroid mice contained fewer β-cells, heterogenous MAFA expression, and increased glucagon(+) and ghrelin(+) cells compared to grafts from euthyroid mice. Taken together, these data suggest that long-term thyroid hormone deficiency may drive the differentiation of human pancreatic progenitor cells toward α- and ε-cell lineages at the expense of β-cell formation.

β1-Adrenergic and M2 Muscarinic Autoantibodies and Thyroid Hormone Facilitate Induction of Atrial Fibrillation in Male Rabbits

Activating autoantibodies to the β1-adrenergic and M2 muscarinic receptors are present in a very high percentage of patients with Graves' disease and atrial fibrillation (AF). The objective of this study was to develop a reproducible animal model and thereby to examine the impact of these endocrine-like autoantibodies alone and with thyroid hormone on induction of thyroid-associated atrial tachyarrhythmias. Five New Zealand white rabbits were coimmunized with peptides from the second extracellular loops of the β1-adrenergic and M2 muscarinic receptors to produce both sympathomimetic and parasympathomimetic antibodies. A catheter-based electrophysiological study was performed on anesthetized rabbits before and after immunization and subsequent treatment with thyroid hormone. Antibody expression facilitated the induction of sustained sinus, junctional and atrial tachycardias, but not AF. Addition of excessive thyroid hormone resulted in induced sustained AF in all animals. AF induction was blocked acutely by the neutralization of these antibodies with immunogenic peptides despite continued hyperthyroidism. The measured atrial effective refractory period as one parameter of AF propensity shortened significantly after immunization and was acutely reversed by peptide neutralization. No further decrease in the effective refractory period was observed after the addition of thyroid hormone, suggesting other cardiac effects of thyroid hormone may contribute to its role in AF induction. This study demonstrates autonomic autoantibodies and thyroid hormone potentiate the vulnerability of the heart to AF, which can be reversed by decoy peptide therapy. These data help fulfill Witebsky's postulates for an increased autoimmune/endocrine basis for Graves' hyperthyroidism and AF.

[Multi-organ failure after massive Levothyroxine ingestion: case report]

Levothyroxine is the drug of choice prescribed worldwide for the treatment of Hypothyroidism. The exact daily dosage, mode of consumption and refractoriness to therapy are still subject of discussion. The intoxication with levothyroxine is rare and with severe complications in adults; on the contrary, high prevalence and benign course is observed in pediatric age. We report the case of a 56 year-old woman, presented to the emergency department after intentional ingestion of massive levothyroxine overdose , with acute renal failure, severe disturbances of cardiovascular and central nervous system, that required intensive care support. In absence of a specific treatment, plasmapheresis has been used with good results, despite important clinical complications. In fact the clinical applications of plasmapheresis are rapidly increasing in number and scope: the plasmapheresis appears to be a very important tool for the treatment of acute and severe forms of thyrotoxicosis due to l-thyroxine intoxication.

[Acute poisoning with levothyroxine in own experience]

Exposure to thyroid products is common, but acute poisonings in adults are rare. Most cases of severe toxicity are related to prolonged, repeated exposure (either inadvertent or deliberate abuse). There are a few reports of toxicity in children following large (greater than 10 mg) single ingestions. Expect significant toxicity in children and adults who have ingested more than 2 to 4 mg of levothyroxine. However, in comorbid elderly patients, the threshold may be lower. In this paper we present acute overdose of levothyroxine in nine adult patients (aged 21-44 years; mean--30.5 years); ingested doses were from 1.2 mg to 15 mg (mean--6.5 mg). Only in three cases (ingested doses were 5.6; 8.0 and 15 mg) minor and mild clinical symptoms were observed and pharmacological treatment was necessary. No severe symptoms were observed in our group. Asymptomatic clinical course in patients who ingested more than 3 mg of levothyroxine probably was related to coingestion of benzodiazepins, beta-blockers, ACE inhibitors and ethanol. Serum free triiodothyronine (T3) level of 20 pg/ml (normal, 4.1 pg/ml) was reported following an overdose of 15 mg levothyroxine in day five. Normalization was observed in day eleven.

Fibroblast growth factor 21 and thyroid hormone show mutual regulatory dependency but have independent actions in vivo

Thyroid hormone (TH) regulates fibroblast growth factor 21 (FGF21) levels in the liver and in the adipose tissue. In contrast, peripheral FGF21 administration leads to decreased circulating levels of TH. These data suggest that FGF21 and TH could interact to regulate metabolism. In the present study, we confirmed that TH regulates adipose and hepatic FGF21 expression and serum levels in mice. We next investigated the influence of TH administration on key serum metabolites, gene expression in the liver and brown adipose tissue, and energy expenditure in FGF21 knockout mice. Surprisingly, we did not observe any significant differences in the effects of TH on FGF21 knockout mice compared with those in wild-type animals, indicating that TH acts independently of FGF21 for the specific outcomes studied. Furthermore, exogenous FGF21 administration to hypothyroid mice led to similar changes in serum and liver lipid metabolites and gene expression in both hypothyroid and euthyroid mice. Thus, it appears that FGF21 and TH have similar actions to decrease serum and liver lipids despite having some divergent regulatory effects. Whereas TH leads to up-regulation in the liver and down-regulation in brown adipose tissue of genes involved in the lipid synthesis pathway (eg, fatty acid synthase (FASN) and SPOT14), FGF21 leads to the opposite changes in expression of these genes. In conclusion, TH and FGF21 act independently on the outcomes studied, despite their ability to regulate each other's circulating levels. Thus, TH and FGF21 may modulate the availability of each other in critical metabolic states.

Thyroxine and triiodothyronine content in commercially available thyroid health supplements

BACKGROUND

As defined by the Dietary Supplement Health and Education Act 1997, such substances as herbs and dietary supplements fall under general Food and Drug Administration supervision but have not been closely regulated to date. We examined the thyroid hormone content in readily available dietary health supplements marketed for "thyroid support."

METHODS

Ten commercially available thyroid dietary supplements were purchased. Thyroid supplements were dissolved in 10 mL of acetonitrile and water with 0.1% trifloroacetic acid and analyzed using high-performance liquid chromatography for the presence of both thyroxine (T4) and triiodothyronine (T3) using levothyroxine and liothyronine as a positive controls and standards.

RESULTS

The amount of T4 and T3 was measured separately for each supplement sample. Nine out of 10 supplements revealed a detectable amount of T3 (1.3-25.4 μg/tablet) and 5 of 10 contained T4 (5.77-22.9 μg/tablet). Taken at the recommended dose, 5 supplements delivered T3 quantities of greater than 10 μg/day, and 4 delivered T4 quantities ranging from 8.57 to 91.6 μg/day.

CONCLUSIONS

The majority of dietary thyroid supplements studied contained clinically relevant amounts of T4 and T3, some of which exceeded common treatment doses for hypothyroidism. These amounts of thyroid hormone, found in easily accessible dietary supplements, potentially expose patients to the risk of alterations in thyroid levels even to the point of developing iatrogenic thyrotoxicosis. The current study results emphasize the importance of patient and provider education regarding the use of dietary supplements and highlight the need for greater regulation of these products, which hold potential danger to public health.

Charcoal hemoperfusion in the treatment of levothyroxine intoxication

BACKGROUND

Levothyroxine (l-thyroxine) intoxication may arise from intentional or accidental ingestion of excessive doses of the hormone and may cause symptoms equivalent to thyroid storm. We report a case of massive accidental l-thyroxine intoxication resulting from an error in the preparation of capsules to treat goiter.

SUMMARY

A 61-year-old woman was admitted showing high levels of thyroid hormones, with serum-free l-thyroxine level of 955.90 nmol/L (74.1 ng/mL) (normal values: 11.61-27.09 nmol/L or 0.9-2.1 ng/mL). It was discovered that she had ingested 50 mg instead of 50 microg/day of l-thyroxine during 9 days. Following charcoal hemoperfusion, the levels of total thyroxine, serum-free l-thyroxine, and triiodothyronine declined dramatically, with a reproducible pattern of reduction in hormone levels observed after each of the three sessions. The patient recovered from her stuporous mental state, atrial fibrillation, and acute respiratory failure.

CONCLUSION

The use of hemoperfusion with a charcoal filter appears to be a very important therapeutic tool for the treatment of acute and severe forms of thyrotoxicosis due to l-thyroxine intoxication.

Minor signs and symptoms of toxicity in a young woman in spite of massive thyroxine ingestion

The serum concentrations of thyroxine, 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine were followed during nine days in a case of acute thyroxine intoxication. On admission the concentrations were 11-12 times, 5-6 times and 16 times the normal mean, respectively. There was a striking discrepancy between the high concentrations of active hormones and the minor clinical symptoms.

Intoxikation mit L-Thyroxin in suizidaler Absicht bei einer Jugendlichen

BACKGROUND

Attempted suicide with l-thyroxine (LT4) is very rare, only being published in some case reports concerning young women. Experiences in the management of LT4 intoxication have already been made because overdosage in infants occurs more often. Guidelines and recommendations depend on the quantity of LT4 that has been ingested.

PATIENT

A 17-year-old girl presented to the pediatric emergency department after intentional ingestion of 20 mg of LT4 20 hours prior to admission. Anamnestically she had increased the thyroxine dose rate up to 800 microg per day during the previous 4 months in order to obtain loss of weight. In spite of massive overdosage and extremely high serum thyroxine levels (fT4 794 pg/ml, TSH suppressed) the girls showed low symptoms and a mild clinical course. Because of tachycardia, hyperhidrosis and muscle tremor propranolol was applied. During the following 22 days fT4 levels returned to normal range and the adolescent was remitted to the outpatient clinic of the department of psychiatry. Whereas patients with graves disease and thyreotoxicosis present with severe symptoms our patient showed a mild clinical course in spite of having extremely high fT4 levels.

CONCLUSIONS

The reasons are ambiguous. A possible answer could be an adaptation in higher fT4 levels in cause of the reported chronic LT4 overdosage.

Seizure in a child after an acute ingestion of levothyroxine

BACKGROUND

Unintentional ingestion of thyroid hormone preparations is a common occurrence reported to poison control centers. These incidents rarely result in serious outcomes. We report a case of a tonic-clonic seizure occurring in a child after ingestion of a maximum of 3.6 mg of levothyroxine.

CASE REPORT

A 3.5-year-old boy ingested up to 41 tablets of 88 microg levothyroxine, which was not discovered until the following day. On the third day after the ingestion, he had a single 5- to 10-minute tonic-clonic seizure. Laboratory results were total thyroxine greater than 24.0 microg/dL; free thyroxine, 5.5 ng/dL; and thyroid-stimulating hormone, 0.03 mU/L. On the following day, the patient had diarrhea and was hyperactive; heart rate was 144 beats per minute, and mild hyperreflexia was noted on neurological examination. Symptoms were resolved 3 days later.

CONCLUSION

This is the second case report of a seizure occurring in a child after an unintentional ingestion of levothyroxine. The maximum amount possibly ingested is much lower than that previously reported. Pediatric ingestion of less than 5 mg of levothyroxine may result in serious outcomes.

[Levothyroxine poisoning: clinical manifestations and therapeutic management]

Intoxication with L-tyroxine has a low prevalence, high prevalence is observed in pediatric age. Toxic dose is unclear, asymptomatic patients have been observed with doses under 5 mg. Systems with high prevalence of symptoms are cardiovascular system, sympathetic nervous system and gastrointestinal tube. Symptoms could appear from hours to days after ingestion. Early hours after L-tyroxine ingestion, levels of T4 and T3 are not related with severity. However, monitoring seric levels is necessary to lead therapeutic approach and to give a prognosis. Daily determinations of T3, T4 and TSH are necessaries. Determinations of temperature, arterial pressure and blood heart rate are needed to control complications. Beta-blockers and intestinal decontamination drugs are used during therapeutic approach. Other therapeutic options are iopanoic acid and propylthiouracil. In summary, intoxication with L-tyroxine could be a severe situation. It is necessary to describe therapeutic protocols in this entity.

Light symptoms following a high-dose intentional L-thyroxine ingestion treated with cholestyramine

Adult exposure to L-thyroxine has a wide range of presentations: most adults either do not develop symptoms or only become minimally symptomatic. Appropriate treatments after exposure to L-thyroxine have yet to be established. A 26-year-old woman with a suicidal intention was witnessed to ingest approximately 50 L-thyroxine tablets, each containing 0.1 mg L-thyroxine (total dose 5 mg). Cholestyramine was administered (4 g every 8 h p.o.). Vital signs were monitored every 6 h and the hormone levels (L-thyroxine and thyroid-stimulating hormone) every 24 h. The thyroxine levels increased, and the thyroid-stimulating hormone levels decreased, with a normalization of the L-thyroxine level on postingestion day 6. Hypertension, dysrhythmias, and delusions did not appear in our patient. Only distal tremor and diaphoresis appeared on day 1 after ingestion. Cholestyramine has been used in cases of iatrogenic hyperthyroidism, in patients with Graves' disease, and in patients with digoxin intoxications, with good responses in all cases and a low incidence of side effects. This case illustrates the potential utility of cholestyramine to treat L-thyroxine intoxications.

Severe symptoms following a massive intentional L-thyroxine ingestion

L-Thyroxine (T4) is commonly prescribed medication for hypothyroidism in humans and animals. Overdose has generally resulted in limited symptomatology managed with sedatives and beta-adrenergic receptor antagonists. We describe the largest acute T4 ingestion ever reported, which resulted in a profound thyrotoxicosis, resistant to treatment. A 34-y-old man ingested 900 (0.8 mg) tablets of veterinary T4 (720 mg) and was given 60 g of activated charcoal. He became lethargic on post-ingestion days 2 and 3; had vomiting, diaphoresis and insomnia on day 4; on day 5 he "looked like he had too much coffee", began "using a lot of words" and became agitated, assaultive and stopped speaking intelligibly; and on day 6 returned to the hospital combative and confused. He was diaphoretic, mydriatic, hyperreflexic, tremulous, with clear lungs and active bowel sounds, and received activated charcoal, haloperidol, diazepam, and phenobarbital, and was tracheally intubated. During hospitalization he was rehydrated, treated with propranolol and diazepam, but remained continuously tachycardic. On day 12 he became afebrile and his tachycardia resolved. Free T4 levels ranged from > 13 mcg/dL on day 6 to 1.2 mcg/dL on day 12. By discharge (day 15) he had lost 20 kilograms of body weight, but was clinically euthyroid 2 w later. This case suggests that large intentional T4 ingestions should be managed differently than current T4 overdose protocol.

Delayed toxidromes

Some toxins do not result in clinical manifestations until several hours after exposure. This article reviews those agents that may cause delayed-onset toxicity. They are organized into four classes: specific pharmaceuticals, biologicals, pharmaceutical dosage forms, and chemicals. There are five basic mechanisms for delayed toxicity: delayed absorption, distribution factors, metabolic factors, cellular and organ capacity effects, and unknown. Scientific evidence for delayed-onset of effects varies considerably among the individual toxins.

[Attempted suicide with 400 thyroxine pills: what happened to the physician-patient relationship?]

Patient aged 49 who developed hypothyroidism after receiving 1131 for relapsing Graves' disease after treatment with propylthiouracil followed by homeopathy. Substitution with thyroxine (0.05 mg/day) was prescribed. Depressed by the perspective of a life long treatment, the patient swallowed 400 pills (20 mg). The evolution was uncomplicated after betablockers administration at hospital. One year later she became euthyroid without further medication. The occurrence of transient hypothyroidism after curitherapy is discussed. The importance of mutual participation in the patient/physician relationship is underlined in the framework of divergent conceptions of medicine.

Thyroxine (T4) metabolism in an athyreotic patient who had taken a large amount of T4 at one time

As we had an opportunity to take blood samples from a totally thyroidectomized patient who had attempted suicide by taking 2,000 microg of Levothyroxine (L-T4), the serum levels of thyroid hormones were sequentially measured to investigate the metabolism of circulating thyroid hormones in an athyreotic human. The serum concentrations of most thyroid hormones reached a peak on the second day, but the serum T3 level showed a peak one day later. The maximum concentrations of T4 (315 microg/l), FT4 (48.8 ng/l) and rT3 (0.80 microg/l) were very high, while the peak T3 level (1.92 microg/l) did not exceed the upper limit of the normal range. The serum T4 and rT3 levels returned to their normal range 13-17 days after the suicide attempt. The TSH level was suppressed rapidly and reached its nadir (0.044 mU/l) on the 6th day. During this period, the T1/2 and MCR of serum T4 were 10.4 days and 0.64 l/day, respectively, which values were almost equivalent to those observed during 15 days after discontinuation of the maintenance L-T4 therapy. In summary, the oral intake of a large amount of L-T4 at one time does not induce a proportional increase in the T3 level in an athyreotic person. The MCR of serum T4 is decreased and the T1/2 of serum T4 is prolonged, probably due to the lack of intrathyroidal deiodination. These findings support the conclusion that the D1 activity in the thyroid is one of the major determinants in the metabolic clearance of serum T4.

Successful treatment of massive acute thyroid hormone poisoning with iopanoic acid

We report a toddler with massive thyroid hormone poisoning in whom the addition of iopanoic acid to the treatment regimen (propylthiouracil and propranolol) resulted in a dramatic clinical and biochemical improvement. Iopanoic acid is a safe and effective drug in the treatment of massive thyroid hormone poisoning in children.

Raising the decontamination level for thyroid hormone ingestions

Ninety-two pediatric cases (age < or = 6 years) of acute thyroid hormone ingestions that were reported over a 20-month period to one American Association of Poison Control Centers (AAPCC)-certified regional poison center were reviewed to determine whether significant toxicity in pediatric patients is associated with acute ingestions of < or = 5 mg levothyroxine (T4) equivalent of thyroid hormone and the highest-tolerated milligram-per-kilogram dose. Parameters evaluated included patient weight, amount ingested, drug preparation, treatment type, outcome, management site, and relevant comments. Eight patients had mild symptoms requiring no specific medical intervention and there was no correlation between the amount ingested and symptoms observed. The maximum T4 dose ingested without gastrointestinal decontamination was 0.13 mg/kg (2 mg). A literature review was also conducted. Only one case of moderate toxicity with a dose of less than 5 mg T4 equivalent was found in the literature review. Significant toxicity is not expected with ingestions of less than or equal to 5 mg T4 equivalent of thyroid hormone.

Kinetics of the pituitary-thyroid axis and the peripheral thyroid hormones in 2 children with thyroxine intoxication

Thyroxine intoxication is a benign, nonfatal condition, relatively common in the pediatric age group. We present here a detailed laboratory follow-up of all thyroidal hormones in 2 healthy girls who inadvertently ingested 2,500 micrograms of L-thyroxine. The two girls were hospitalized and treated with ipecac, gastric lavage, propranolol, prednisone, cholestyramin and propyl-thiouracil. All physical signs were normal and no symptoms were reported. All thyroidal hormones were measured 12 times from 2 h to 20 days after the ingestion. For T4, T3, rT3 and thyroglobulin (Tg) a one-compartment kinetic model was formulated and fitted to the empirical data. The kinetic data constants of production and elimination were calculated, as well as the metabolic clearance rate. All laboratory values were similar in both girls. T4 serum levels were already high 2 h after the intoxication and returned to normal values only after 13 days. Fitting the T4 serum levels with a one-compartment model resulted in absorption and degradation constants similar to those in normal adult subjects. Thyroid-stimulating hormone (TSH) levels decreased reaching their lowest concentration 14 h after the intoxication. They remained low till the 4th day, after which they rose gradually. Twenty days after the intoxication, TSH levels were still below their initial values. T3 reached its peak levels 11 h after the ingestion and decreased to normal values after 3 days. Both T3 production constants and T3 degradation constants were significantly increased. rT3 reached its peak level on the 2nd day after the intoxication and decreased to normal values on the 4th day. Its production and degradation constants were somewhat below normal levels. The T3/rT3 ratio decreased from a normal level of around 3 to as low as 1 and rose again after 13 days to extremely high levels (as high as 8). Tg serum levels dropped continuously with a half-life of 1-5 days and started rising again after 2-13 days. In conclusion, T4 intoxication in the child is combated primarily by a significant increase in T3 production and degradation, while meticulously maintaining relatively low T3 levels.

Acute overdose of levothyroxine in a dog

An overdose of up to 850 levothyroxine sodium tablets (0.2 mg) in a healthy 6-year-old 16.8-kg dog induced an episode of vomiting and hippus within 9 hours of ingestion. The dog was treated with activated charcoal and saline (magnesium sulfate) cathartic. Initially the serum concentration of thyroxine (T4) 4,900.9 nmol/L. On the second day, serum concentration of triiodothyronine (T3) was 5.3 nmol/L. Serum T4 concentration decreased slowly and was not determined to be normal until day 36. Serum T3 concentration was found to be normal on day 6. Serum alanine transaminase activity peaked on day 6 at 345 U/L. Significant abnormalities were not found during the following 36 days. Clinical signs of thyroid hormone toxicosis in dogs and cats include hyperactivity, lethargy, tachycardia, tachypnea, dyspnea, abnormal pupillary light reflexes, vomiting, and diarrhea. High overdoses of levothyroxine sodium in dogs should be managed by initial decontamination and administration of activated charcoal with a cathartic followed by supportive care.

Acute L-thyroxine overdose; therapy with sodium ipodate: evaluation of clinical and physiologic parameters

Two children with acute L-thyroxine overdose were treated with sodium ipodate, an oral cholecystographic agent. Initial thyroxine (T4) levels were elevated to 98.5 mcg/dL and 134.1 mcg/dL, with associated triiodothyroxine (T3) levels of 354 ng/dL and 402 ng/dL. T3 levels increased to a maximum of 662 ng/dL and 468 ng/dL. With administration of sodium ipodate, the T3 decreased with a simultaneous increase of rT3 level. Sodium ipodate effect lasted 72 hours. No toxic effect was noted. Interestingly, thyroid hormone levels correlated with systolic blood pressure but with no other physiologic parameter. Sodium ipodate appears to be a viable treatment modality for acute thyroid overdose in children.

Full recovery following massive overdose with insulin and thyroxine

Specific treatment is available for only a few substances taken in overdose. We report here a patient who attempted suicide with a massive overdose of insulin and thyroxine, a combination not previously reported, and discuss the specific treatments given to mitigate the harmful effects of this combination.

[Acute poisoning with thyroxine in children]

Two girls aged 5 and 14 years were admitted to hospital after ingestion of L-thyroxine in estimated doses of 72 micrograms.kg and 118 micrograms.kg in the preceding 4 and 8 hours, respectively. Both had high serum T4 (19 and 20 micrograms/dl) and were asymptomatic at the time of admission and both were treated with Iopanoic acid 3 g orally every 72 hours, in order to block the conversion of T4 into T3. Serum levels of T4 were still elevated for up to ten days (8 and 16 micrograms/dl, respectively at day 10), but serum levels of T3 came down to 60 micrograms/dl within the first 48 hours of treatment in both cases. It should be taken into account that these patients may be initially asymptomatic and that symptoms may appear even later than 24 hours after the ingestion, so they should be admitted and treated at hospital. Iopanoic acid has been proved to be a treatment of choice in order to block the conversion of T4 into T3.

[Male sexual behavior in thyroxine toxicosis]

A shortening of mounting latency and postejaculatory period revealed an activation of sexual behaviour's motivational components in thyroxin toxicosis in male rats. A negative correlation was found between the postejaculatory period duration and the thyroxin level. The estradiol concentration increased whereas the testosterone one decreased in rats and was followed by a lowering of ejaculations in the test. The serotonin contribution to the mechanism of activation of sexual behaviour's motivational component in thyroxin toxicosis, is discussed.

Massive levothyroxine ingestion. Conservative management

The clinical course of a 29-month-old girl who was referred for evaluation after ingesting ninety 0.2-mg tablets of levothyroxine is reported. Despite an initial thyroxine (T4) level of 282 micrograms/dl and a triiodothyronine (T3) level of 1,837 ng/dl at 48 hours postingestion, her symptoms were mild and included irritability, vomiting, tremor, and tachycardia. Treatment was limited to activated charcoal and propranolol. Thyroid hormone levels fell to normal by 13 days postingestion. The child's clinical course was benign. Even after massive acute ingestions of levothyroxine, children's symptoms are usually mild and may be controlled with propranolol. This conservative approach should be considered before expensive and potentially dangerous therapies are undertaken.

Acute thyroxine ingestion in pediatric patients

During a 1-year period, 15 cases of acute thyroxine (T4) overdose with documented serum T4 concentrations were studied. All patients were less than 5 years of age and 80% were boys. All were examined within 1 to 6 hours of ingestion and all were asymptomatic. Estimated dose ingested in 10 patients ranged from 1.5 to 8.8 mg (0.1 to 0.73 mg/kg). Three patients with initial T4 serum concentrations greater than 75 micrograms/dL manifested signs of toxicity within 12 to 48 hours (fever, tachycardia, hypertension, and/or agitation) that resolved within 24 to 60 hours. The mean elimination half-life of T4 in 7 patients with multiple serum concentrations was 2.8 +/- 0.4 days, whereas the mean elimination half-life of triiodothyronine was 6 +/- 1.7 days. It was concluded that (1) the majority of acute pediatric T4 overdoses are not severe and may be managed on an outpatient basis, (2) the absence of early clinical manifestations does not preclude delayed onset of toxicity that may be better predicted by initial T4 concentrations, and (3) the elimination half-life of T4 is shorter and the elimination half-life of tri-iodothyronine is longer than with therapeutic doses.

Clinical effects of accidental levothyroxine ingestion in children

Forty-one children, aged 1 to 5 years, who accidentally ingested levothyroxine sodium were studied. Symptoms possibly associated with the ingestion occurred in 11 patients (27%). These symptoms (tachycardia, hyperactive behavior, fever, vomiting, diarrhea, diaphoresis, and flushing) were categorized as minor and all resolved without treatment. Because observed effects were generally mild and often unrelated to either estimated amounts of hormone consumed or serum thyroxine levels, a conservative approach to patient treatment is recommended in cases of levothyroxine ingestion in children.

Massive thyroxine intoxication: evaluation of plasma extraction

Six patients were admitted after erroneous massive intake of levothyroxine (70-1200 mg over an interval of 2-12 days). All patients developed classical symptoms of thyrotoxicosis within 3 days of the first dose; five patients presented grade II-III coma and one became stuporous (days 7-10). Two patients developed left ventricular failure and three had arrhythmias (days 8-11). Total thyroid hormone levels in serum on admission ranged 935-7728 nmol/l for T4 (TT4) and 23-399 nmol/l for T3 (TT3). All patients received treatment with hydrocortisone and Propranolol. Propylthiouracil was also given in 3 cases. Extractive techniques (charcoal haemoperfusion and/or plasmapheresis) were initiated 8-14 days after the first dose of L-T4. The plasma disappearance rate (K) of TT4 with plasmapheresis was 30 times higher, on average, than under standard medical treatment (M). Also, K of TT4 under haemoperfusion was about five times higher than K under M. K changes for TT3 were higher under haemoperfusion than under plasmapheresis. Furthermore, extractive procedures shortened the average half life of TT4, (from 106.5 +/- 44.6 to 59.7 +/- 20.2 h, p less than 0.05).

[Acute factitious hyperthyroidism--moderate clinical symptoms in 3 cases under beta-blocker treatment]

The clinical and laboratory findings are described in three patients who ingested large amounts of L-thyroxine (two cases) and L-thyroxine together with L-triiodothyronine and who were treated with propranolol. Serum concentrations of thyroxine (maximum values 75 micrograms/dl, 64 micrograms/dl, and 20 micrograms/dl, respectively; normal range 4-12 micrograms/dl), triiodothyronine (maximum values 837 ng/dl, 453 ng/dl, and 566 ng/dl, resp.; normal range 80-180 ng/dl), reverse triiodothyronine (maximum values 235 ng/dl, 190 ng/dl, and 65 ng/dl, resp.; normal range 10-40 ng/dl) as well as free thyroxine equivalent and free triiodothyronine equivalent were monitored daily until they reached the normal range. Statistical analysis of the kinetics of these parameters indicated that the extreme thyroxine conversion was directed toward reverse triiodothyronine, partly due to the treatment with the beta-adrenergic blocker propranolol. The striking discrepancy between the high concentrations of the active hormones and the moderate clinical symptoms was most likely caused by peripheral effects of propranolol.

Benign course after massive levothyroxine ingestion

Management of thyroid hormone ingestion is controversial. We present nine children with massive levothyroxine ingestion who experienced a benign course. Their serum thyroxine levels ranged from 19.9 to 84.7 micrograms/dl. Seven were clinically euthyroid, and the other two had mild symptoms. No specific therapy was given. We recommend gastrointestinal decontamination procedures and serum thyroxine levels for an ingestion of greater than 2.0 mg of levothyroxine (or its equivalent). If levothyroxine has been ingested, neither immediate hospitalization nor prophylactic antihyperthyroidism therapy is recommended. If the initial serum thyroxine level is significantly elevated, close outpatient follow-up, especially during days three to 10, is warranted. However, massive ingestion of thyroid extract or triiodothyronine may require immediate hospitalization for observation. Therapeutic interventions aimed at extracorporeal removal of excess thyroid hormones are not recommended. Specific antithyroid therapy should be reserved for those rare patients with significant symptoms of thyrotoxicosis.

Levothyroxine ingestions in children: an analysis of 78 cases

A series of 78 cases of accidental levothyroxine ingestion in children (less than 12 years old) with treatment limited to ipecac-induced emesis and a single oral dose of activated charcoal is presented. No patient received any form of dialysis or hemoperfusion, propylthiouracil, cholestyramine, steroids, or serial doses of oral activated charcoal. Propranolol was used in one case despite the absence of clinical manifestations of toxicity. Only four children developed symptoms, limited to modest fever (38.3 degrees C), supraventricular tachycardia (120-176 beats/min), lethargy, irritability, vomiting, diarrhea, and abdominal pain. Peak T4RIA values in three patients were 32.8, 30.0, and 26.4 micrograms/dl, respectively, and two of these patients remained asymptomatic. Initial therapy for acute levothyroxine ingestions in children can be safely limited to routine gastrointestinal decontamination. Hospitalization or prophylactic treatment with propranolol, propylthiouracil, corticosteroids, cholestyramine, or extracorporeal detoxification are unnecessary in the early asymptomatic phase.

[Role of the thyroid hormone in the functioning of the hypophyseal-adrenal-gonad system of rabbits]

The influence of a long-term T4 injection on the gonadal and adrenal androgenic function as well as on the hypophyseal gonadotropic activity was studied in experiments on adult male rabbits, using histological and hormonal methods. It was shown that in rabbits with experimental moderate thyroxin toxicosis the testicular testosterone secretion is inhibited, whereas the adrenal testosterone secretion is compensatory enhanced. The level of hypophyseal gonadotropins tends to rise. The prostatic weight is lowered, but the glandular epithelial cells retain the ability of secreting. The thyroid hormone role in the hypophyseal-adrenal-gonadal function in health and hypothyrosis is discussed.