Thyrotoxicosis causes

Have you ever heard of Hamburger Thyrotoxicosis?  Can your Burgers become a Thyroid Danger? Is it possible that your hyperthyroidism is caused by eating hamburgers?

Canadian researchers looked at recurrent episodes of transient thyrotoxicosis (severe hyperthyroid episodes) that went on over in a 61 year old woman. They found rapid weight loss, palpitations, increased sweating, a heart rate of 112 beats/minute and tremor in her hands. She was diagnosed as hyperthyroid which was confirmed by an free elevated T4 level of 46 [normal range 9 to 23] and low thyroid-stimulating hormone TSH of 0.02. Within 8 weeks, her symptoms went away on their own, and her free T4 returned to normal. 

This was the woman’s fifth 2-3 month long episode of transient hyperthyroidism over an 11-year period. She did not have thyroid antibodies, so her physicians were puzzled. They questioned the woman about use of herbal supplements or thyroid supplements in some form, but she denied taking anything similar.

So what causes thyrotoxicosis?

The mystery was solved, however, when additional questioning into the woman’s dietary history showed that she lived on a farm with her husband. Every few years, they slaughtered a cow from their herd, which was their main source of meat. After discussions with the couple’s butcher, it was discovered that he did now know about the prohibition against what’s called “gullet trimming.” (In gullet trimming, muscles from the bovine larynx are harvested, and can include thyroid tissue.) 

The butcher was using meat from the neck of the patient’s cows to make patties, which were usually consumed by the woman within a couple of months of butchering. Her husband did not suffer any thyroid problems, as he preferred other cuts of meat and didn’t eat the patties.

 Interestingly, community-wide outbreaks of thyrotoxicosis were caused by eating cow thyroid in ground beef in Minnesota, South Dakota and Iowa in 1984 and 1985. These outbreaks resulted in the prohibition of gullet trimming in all plants that slaughter cattle and pigs. When inexplicable thyrotoxicosis occurs, the possibility of exposure to animal thyroid, via access to meat from slaughtered farm animals or hunting game should be considered. 

Source: Parmar MS, et. al. “Recurrent hamburger thyrotoxicosis,” CMAJ. 2003 Sep 2;169(5):415-7.

Thyroid hormones are orally active, which means that consumption of thyroid gland tissue can cause thyrotoxicosis, a type of hyperthyroidism. Several outbreaks of thyrotoxicosis have been attributed to a practice, now banned in the US, called “gullet trimming”, where meat in the neck region of slaughtered animals is ground into hamburger. Because thyroid glands are reddish in color and located in the neck, it’s not unusual for gullet trimmers to get thyroid glands into hamburger or sausage. People, and presumably pets, that eat such hamburger can get dose of thyroid hormone sufficient to induce disease. 

A report by Hedberg and colleagues (1987) on this topic is one of several in the literature. They described an outbreak of thyrotoxicosis in Minnesota and South Dakota that was traced to thyroid-contaminated hamburger. A total of 121 cases were identified in nine counties, with the highest incidence in the county having the offending slaughter plant. The patients complained of sleeplessness, nervousness, headache, fatigue, excessive sweating and weight loss. For patients with features suggestive of silent thyroiditis, health care providers should consider this cause of hyperthyroidism, especially for anyone who may be slaughtering farm animals for their own use and for hunters who may be gullet trimming game.

Bottom line- watch out what you eat, because this can cause you Hyperthyroidism as well!

Thyrotoxicosis Treatment- What do you need to know and doctors don’t have time to tell you?

Thyrotoxicosis or Hyperthyroidism is the clinical syndrome caused by an excess of circulating free thyroxine and free triiodothyronine, (FT3 and FT4) or both. It is common, affecting about 2% of women and 0.2% of men. (For more information about test- TSH, FT3, FT4- check here>>>>>

Causes

Of all the causes of thyrotoxicosis, Graves’ disease is the most common (70-80%); toxic thyroid adenoma, toxic multinodular goitre, and subacute thyroiditis are the second of importance when considering the causes for thyrotoxicosis.

Causes of Thyrotoxicosis

Common causes:

Graves’ disease

Toxic multinodular goiter

Toxic nodule

Thyroiditis

Subacute Postpartum Silent

Factitious hyperthyroidism (administration of thyroxine or triiodothyronine)

Rare

Exogenous iodide (Jod-Basedow phenomenon)

Radiographic contrast agents

Health food preparations

Drugs (amiodarone)

Iodinisation programmes

Neonatal hyperthyroidism

Excess secretion of thyroid stimulating hormone

Pituitary adenoma Pituitary resistance to thyroxine and triiodothyronine

Metastatic thyroid cancer

Struma ovarii

and some other not so typical reasons.

Clinical features of thyrotoxicosis

Thyrotoxicosis usually develops insidiously, and most patients have had symptoms for at least 3-6 months before presentation. Almost every system is affected, and patients may initially present to various medical specialists – for example, to a cardiologist with atrial fibrillation, or to a neurologist with myopathy.

When thyrotoxicosis is suspected, the diagnosis should be confirmed by measurement of thyroid stimulating hormone (TSH) and free thyroxine in the serum, which are usually present in low and high concentrations respectively.

The concentration of thyroid stimulating hormone may, however, be normal or increased if the cause of thyrotoxicosis is either a pituitary adenoma secreting thyroid stimulating hormone or resistance to thyroid hormone.

In the latter case the patient is clinically euthyroid. Estimation of total thyroxine concentration is not useful and may be misleading as various factors, including pregnancy, cirrhosis of the liver, and opiate drugs, alter the binding of thyroxine to thyroxine binding globulin.

When the concentration of thyroid stimulating hormone is low but that of thyroxine normal, serum concentration of free triiodothyronine should be measured to diagnose triiodothyronine (T3) toxicosis. Thyroxine (T4) toxicosis (raised concentration of free thyroxine, normal concentration of free triiodothyronine), which is unusual, may occur with high iodine intake, treatment with amiodarone, severe intercurrent illness, or starvation. Finally, euthyroid patients with Graves’ ophthalmopathy, severe non-thyroidal illness, large goitres, or those who have had recent treatment for thyrotoxicosis may have a suppressed concentration of thyroid stimulating hormone.

Thyrotoxicosis treatment

Antithyroid drugs: Carbimazole, Methimazole and Propylthiouracil constitute the thionamide group of antithyroid drugs. Propylthiouracil is considered the safest drug among all of them and it is even prescribed to pregnant women.

They inhibit the excess iodide and coupling of iodothyronines, thus reducing production of triiodothyronine and thyroxine.

Propylthiouracil also inhibits the peripheral conversion of thyroxine to triiodothyronine. In addition to blocking thyroid hormone biosynthesis, these drugs also lower concentrations of thyroid stimulating hormone receptor antibodies and increase activity of suppressor T cells, which suggests that they have immuno- suppressive effects.

Carbimazole is given once daily, which makes it the drug of first choice, eventually. Once patients are taking a maintenance dose, serum concentrations of free thyroxine and thyroid stimulating hormone (TSH) are measured every three months.

The duration of antithyroid treatment has been much studied and debated (6-24 months), but is usually 18 months, even though I know people on thyroid medication for years.

Beta Blockers

These are useful for treating some of the clinical features, such as tremor, palpitations, and anxiety. Propranolol (120-240 mg/day) is the most commonly used beta blocker, although any could be used. Once a euthyroid state has been reached, the b blocker is discontinued.

Summary  for Thyrotoxicosis Treatment/ Hyperthyroidism

• Graves’ disease is the commonest cause of thyrotoxicosis
  
• It is an autoimmune disease: the thyrotoxicosis is caused by the presence of thyroid stimulating antibodies
• Eyes and skin may be commonly affected
• Initial treatment is with carbimazole (methimazole) or propylthiouracil, together with the use of a blocker for the first 4-6 weeks

Patients should be warned of the side effects of antithyroid drugs, however they are not typical.