Risk Factors, Interventions and Treating Nutritional Deficiences for Hypothyroidism

Abstract

Hypothyroidism is a thyroid hormone deficiency. Risk factors include age, race, sex, and geographic location. Assessment and interventions differ between Western and functional practitioners, but treating other nutritional deficiencies may help to treat hypothyroidism.

Etiology

Hypothyroidism is defined is a thyroid hormone deficiency in which cellular metabolism is lowered in the body.  Only second to diabetes, thyroid disease is the most prevalent endocrine disorder affecting 1-10% of the population.¹  Primary hypothyroidism is most commonly caused by autoimmune thyroiditis (Hashimoto’s Thyroiditis) in Western society, but in other parts of the world, iodine deficiency is predominately responsible. Other origins of hypothyroidism are thyroidectomy, radioiodine therapy, and treatment with drugs like amiodarone, lithium, thionamide, excessive iodine interferon, sunitinib, rifampicin, and thalidomide.²  In postpartum women, hypothyroidism may be transient and up to 85% of women regain their normal thyroid function. In newborns, congenital hypothyroidism occurs in one in 4000.  Overt hypothyroidism is defined as having serum thyroid stimulating hormone (TSH) that is above the reference range and low free thyroxine (fT4). Subclinical hypothyroidism is characterized as having elevated TSH but fT4 is within normal range.²

Epidemiology

Although common around the world, hypothyroidism is exceptionally common in the UK and India. The NHANES III study found the global incidence of hypothyroidism is at 4.6%   In countries with sufficient iodine intake, 1%-2% of the population has hypothyroidism with as high as 7% in people ages 85-89 years old. In the USA, 0.3% are affected while in Europe it ranges from 0.2%-5.3% of the general population. In Australia, the rate was reported up to 4.2%. White and Hispanic individuals had similar occurrences, but people of Afro-Caribbean descent were much lower at 1.7%.  There are limited data from the Middle East on hypothyroidism but in Tehran, where iodine levels are sufficient, the rate of occurrence is 7.62 and 2.0 per 1000 people with subclinical and overt hypothyroidism. In 16% of women and 8% of men, thyroid antibodies were discovered, which is similar to data from European studies. In sub-Saharan Africa, hypothyroidism is rare and found mostly in patients with HIV who were taking drug treatment regimens for tuberculosis. In China, there has been an increase in subclinical hypothyroidism, going from 3.22% to 16/7/5 and an increase in person with thyroid peroxidase antibodies form 9.81% to 11.5%. India has rates of hypothyroidism as high as 10%. Inland areas reported higher occurrences than coastal areas, even though there has been an increase in salt iodization. Endocrine disruptors may play a part in the increase in cases.³

Risk Factors

There are several risk factors for hyperthyroidism.  Being female is one of the highest risk factors for developing subclinical hypothyroidism. Women have more than double the rate of occurrence than men with 6%t to 10% compared to men with 2% to 4%. One of the most significant risk factors for hypothyroidism is age. Up to 20% of females older than 60 have been documented with subclinical hypothyroidism. Women 45 and older showed a higher occurrence.  Possible reasons for the increase in subclinical hypothyroidism are a decrease in TSH biological activity, decreased  the sensitivity of the thyroid gland to THS and decreased thyroxine turnover as a result of aging.⁴

Excessive iodine intake can have a toxic effect and decrease thyroid function. In iodine-sufficient regions, subclinical hypothyroidism is more common than in iodine-deficient regions. Racial differences contribute to the risk of developing subclinical hypothyroidism.⁴

In the United States, studies have shown that in whites, concentrations of serum TSH were higher than in blacks.⁴ The temperature may contribute to changes in TSH. In a study in Korea, which has a considerable difference in temperature between winter and summer, TSH increased during the winter and spring seasons and decreased during the summer and fall seasons. This could be attributed to adaptive thermogenesis and changes in photoperiod which could affect melatonin which regulates many neuroendocrine pathways.⁴

Cigarette smoking may have a protective factor regarding subclinical hypothyroidism “through competitive inhibition of phytotoxic iodine binding to sodium-iodide symporter in thyroid follicular cells, thiocyanate inhibits iodide transport, organification and release of thyroid hormone from the thyroid gland” ⁴

Risk factors with Hashimoto’s Thyroiditis include excess iodine intake, low selenium levels, and iron deficiency. Selenoproteins are essential to thyroid action are anti-inflammatory in Hashimoto’s Thyroiditis risk. They may also reduce thyroid peroxidase antibodies. Hashimoto’s patients are commonly iron deficient which may be due to autoimmune gastritis which inhibits iron absorption. Lower vitamin D has been observed in people with Hashimoto’s Thyroiditis, possibly connecting a deficiency to the disease.⁵

Dietary factors may lead to thyroid dysfunction. Goitrogens found naturally in foods like legumes, groundnuts, and raw forms of cabbage, cauliflower, broccoli, turnip, and cassava along with soy or foods enriched with soy can reduce the absorption of T4 can increase Hashimoto’s Thyroiditis. When cooked the goitrogens are destroyed, making them safer for consumption.⁵

Excess dietary fat may lead to higher total and free thyroxine levels. High doses of green tea extract may increase TSH levels.⁶ Environmental factors that can affect the thyroid are organochlorine compounds which are found in pesticides, Polychlorinated biphenyls, polybrominateddiphenylethers, bisphenol-A, triclosan, perchlorates found in rocket fuels, cosmetic with UV filters, and heavy metals like cadmium and lead. ⁶

Assessment

A patient may present with multiple symptoms indicating hypothyroidism. Some symptoms are fatigue, cold intolerance, dry skin, voice hoarseness, cognitive impairment, weight gain, constipation, hair loss, bradycardia, and facial periorbital edema. Although some patients with subclinical hypothyroidism will not have symptoms, nearly 30% will present with symptoms. In Western medicine, testing starts with serum TSH and FT4. If the patient has a TSH within normal range, which is 0.4-4.0 mU/1 and falls along the upper limit and FT4 is normal, the patient is considered subclinical.⁷  Free triiodothyronine (FT3) is recommended to rule out hyperthyroidism if it’s too high and if it’s too low,  indicate whether Hashimoto’s may be the cause.  Thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) are tested if Hashimoto’s Thyroiditis is suspected.⁸   There is limited documented research regarding the functional medicine thyroid lab standards, but anecdotally, testing for the full panel of thyroid labs is preferred to detect subclinical levels and Hashimoto’s Thyroiditis earlier. In addition, functional medicine practitioners often test for Reverse T3 (RT3) to assess the conversion of T4 to T3. Another difference between Western and functional assessment is the reference range used to diagnose hypothyroidism.  Functional practitioners tend to use a range for TSh of 1-2 UIU/ML which is lower than traditional Western Medicine Practitioners.⁹

Interventions

 Natural desiccated thyroid made from the thyroid gland of a pig was the first therapeutic intervention for hypothyroidism. It contains both T4 and T3. It has been replaced as first-line therapy by levothyroxine, a synthetic T4, a monotherapy. With LT4 the body converts some of it to T3. Some patients are also given liothyronine (LT3) which is a synthetic form of T3 if they don’t overt T4 well.  Issues with synthetic LT4 is that patients may have normal TSH levels while being treated but still report hypothyroid symptoms. In one study 48% of patients preferred natural desiccated thyroid over LT4.¹⁰  Nutritionally, an autoimmune paleo diet has shown promise in decreasing inflammation, modulating the immune system and symptom relief for women with Hashimoto's Thyroiditis.¹¹ As stated earlier, iodine and selenium deficiency may contribute to deficiencies that lead to hypothyroidism. A recent review emphasized the need for checking serum levels of iodine, selenium and vitamin D in the case of Hashimoto’s and emphasized the importance of a low or no gluten diet even when the patient doesn’t have celiac disease.¹²  Stress management may also help to decrease anti-thyroglobulin antibodies in women with Hashimoto’s through lifestyle changes, diaphragmatic breathing, relaxation techniques, cognitive reconstruction, diet changes, and guided imagery.¹³

Conclusion

Hypothyroidism can be caused by autoimmune, dietary or environmental reasons. From a functional standpoint, complete thyroid panel testing would be advised when a patient presents with one or more symptoms. Additionally, nutritional testing for vitamin deficiencies is advised. Combination T4/T3 therapy along with dietary and lifestyle changes to manage stress would be the protocol that takes a holistic approach to patient care.

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