YOUR THYROID HORMONES

Your thyroid glands are located at the lower front part of your neck and plays a crucial part in maintaining your body’s metabolism.

Your pituitary gland produces the thyroid stimulating hormone (TSH) and secretes it to the thyroid gland. The thyroid gland produces two hormones: Thyroxine *T4) which is very much inactive and is in large component of what the thyroid gland produces and triiodothyronine (t3) - a more active form but not produced as much as your thyroid glands.

Thyroxine (t4) is converted to T2 at cell level. The cells use T3 for its functions.

The amount of T4 that is in the blood is regulated by the pituitary gland. If the pituitary gland sees a lot of T4 in the blood, it will switch off its production. If there is too little t4 in the blood, the pituitary gland will increase its production. Around 1-10% of the general population have thyroid disorders. This increases to around 25% in the older population.

The Balance of Thyroid Hormones Is Important

Having an optimal thyroid function is crucial for effective metabolism.

Too little or too much of the thyroid hormones affect your metabolism significantly.

Hyperthyroidism

If you are producing too much T4 (called hyperthyroidism), your heart may beat faster, you may have diarrhoea or weight loss. You may have trouble tolerating heat or even have mood swings or hand tremors. When the thyroid gland produces too much T4. The pituitary gland decreases production of TSH.

Causes of hyperthyroidism may be:

-        Having too much iodine

-        Having thyroiditis (inflammation of thyroid glands)

-        Taking to much of the medication for thyroid replacement (that’s why regular monitoring is important).

-        Having Graves’ Disease where your immune system attacks your thyroid glands.

-        At times, there is secondary pituitary failure (for example, in a forward movement in a concussion where the pituitary gland can get damaged due to the impact of the motion).

In chronic cases, you may develop goiter, which is enlarged thyroid gland.

 Diagnosis of hyperthyroidism can be made by either physical examination by the health provider, thyroid hormone test such as TSH, T4, T3 and thyroid antibodies or through imaging or radioactive iodine update rate.

Hypothyroidism

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones that your body needs. In this case, the T4 levels are low and so the pituitary gland increases TSH levels (making this high).

Hypothyroidism can occur due to the following reasons:

-        Hashimoto’s disease where the body’s immune system targets the thyroid gland

-        Thyroiditis – inflammation of thyroid

-        Pituitary disorder

-        Too little or too much iodine in your diet

-        Effect of radiation on the thyroid gland

-        As a result of surgery

-        As a result of birth defect (congenital hypothyroidism).

To little of the thyroid hormone can cause weight gain, fatigue, constipation, puffiness, dry thinning hair, trouble tolerating cold dry skin, heavy or irregular menstrual cycle.

Thyroid Antibodies

Antibodies are proteins produced by your immune system to fight against foreign substances like bacteria and viruses. However at times, the body can produce antibodies to fight its own cells, tissues and organs (known as autoimmune disease).

There are different thyroid antibodies. Some can attack the thyroid gland, others can cause the thyroid glands top produce more of certain thyroid hormones.

There are three thyroid antibodies:

• Thyroid peroxidase antibody (TPO)—the most common test for autoimmune thyroid disease; it can be detected in Graves disease or Hashimoto thyroiditis.
• Thyroglobulin antibody (TGAb)— this antibody targets thyroglobulin, the storage form of thyroid hormones.
• Thyroid stimulating hormone receptor antibodies (TSHRAb)—includes two types of autoantibodies that attach to proteins in the thyroid to which TSH normally binds (TSH receptors):

• Thyroid stimulating immunoglobulin (TSI) binds to receptors and promotes the production of thyroid hormones, leading to hyperthyroidism.
• Thyroid binding inhibitory immunoglobulin (TBII) blocks TSH from binding to receptors, blocking production of thyroid hormones and resulting in hypothyroidism. This antibody is not routinely tested.

Dietary Consideration for Healthy Thyroid Health

A balanced diet that provides key nutrients such as Selenium, Zinc and Iodine is needed to have a good thyroid health. To ensure that you have sufficient iodine in your diet, use iodised salt, have fish, seafood and diary products regularly. Seawood is also a good source of iodine but should be used in very small amounts to ensure that there is no toxicity or overdose.

Bread is also fortified with iodine (except for homemade, salt free or organic types).

NZ soil is low in Selenium thus Selenium content in NZ food is low. However, sources of Selenium include eggs, diary foods, organ meats (such as kidney and liver), seafood and imported cereals. Brazil nut (from Brazil which has good amount of selenium in its soil) is also a good source of selenium.

However, in autoimmune disease such as Graves or Hasimoto’s, it is crucial not to overdose with iodine as this may be counterproductive to treatment.

There are also another components of dietary management of these diseases, so having an individualised consultation with Clinical Dietitian-Nutritionist is recommended for the management of these.

Maximised Nutrition recommends that appropriate supplementation is only undertaken after a Clinical Dietitian-Nutritionist assessment so as to avoid over dosing or toxicity.

References

 https://www.thyroid.org/thyroid-function-tests/
2.     https://medlineplus.gov/hyperthyroidism.html
3.     https://medlineplus.gov/hypothyroidism.html
4.     https://www.labcorp.com/help/patient-test-info/thyroid-antibodies

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