Sunday, March 18, 2012

Hypothyroidism

The thyroid gland is a butterfly-shaped endocrine gland that sits on the lower front of the neck. It is the body's internal thermostat and produces the thyroid hormones (TH), Thyroxine (T4) and Triidothyronine (T3). T4 is produced solely in the thyroid gland, whereas T3 is produced both from the thyroid as well as conversion from T4.
Thyroid hormones are essential in order for every cell in our bodies to work. They act on cells to control oxygen consumption, heat production, and even protein synthesis (6). Hence, they regulate our body temperature, our caloric burning rate; and also our energy consumption in supporting the brain, heart, muscles and other organs in working condition.   
Production of TH is controlled by interactions between the Hypothalamus (located in the middle of our brains), the Pituitary gland (a pea sized gland at the base of our brain) and the Thyroid gland (5). The hypothalamus releases hypothalamic hormones, called Thyrotropin-releasing hormone (TRH), which signals the pituitary gland to secrete pituitary-thyroid-stimulating hormone (TRH). TRH communicates with receptors on thyroid tissue to stimulate secretion of the TH. About 80% of hormones produced in the thyroid gland are T4, and about 20% are T3. In return, the fluctuating levels of TH circulating in our blood form a "feedback loop" signaling the pituitary gland, and perhaps even the hypothalamus, to release appropriate amounts of TSH, thereby maintaining a stable level of TH in our blood stream.
What is Hypothyroidism and its Symptoms?
Hypothyroidism is a condition where the thyroid gland is under active ("hypo" means "under"); and hence, insufficient TH are being produced to meet the body's needs, causing bodily functions to wind down. 
According to the American Thyroid Association (1), the effects of this "slow down" can be multifold, causing overt symptoms and sometimes, more dangerous but less obvious ones. To give you a few examples, as less heat and energy are produced, our brain and even the bowels might move at a snail's pace. Therefore, problems with memory and depression could set in, or one could become constipated. In addition, one might also experience changes that cannot be sensed, like elevated blood pressure and cholesterol levels, due to a sluggish and backed up blood flow.
Most common symptoms of hypothyroidism include: intolerance to cold, chronic fatigue, low body temperature, slow heart rate. Hypothyroidism could also present itself as: easy weight gains, irritability, loss of appetite, muscle weakness/cramps, dry scaly skin, painful premenstrual syndromes, heavy periods, hair loss, recurrent infections, migraines, even fertility problems, yellow-orange skin, puffiness around face/hands/ankles, carpal tunnel syndrome. 
What could be some causes of Hypothyroidism?
Hypothyroidism can be differentiated into primary and secondary hypothyroidism. Primary hypothyroidism is a direct consequence of a disorder in the thyroid gland causing failure in the synthesis and secretion of TH. 
On the other hand, secondary hypothyroidism is a consequence of the failure on the part of the pituitary gland to release sufficient TSH; OR from the failure of the hypothalamus in producing TRH. Since TSH and TRH regulate the production of TH, decreased levels of either will naturally lead to corresponding decreases in the production of TH (2).
Some causes of primary hypothyroidism include Autoimmune Disease, Thyroiditis (Inflammation of the thyroid), Iodine deficiency or excess, surgical removal of the thyroid gland, radiotherapy, drugs, congenital factors (born with it). The most common cause of hypothyroidism is autoimmune disease, and it affects more women than men (elaboration to follow in later paragraphs).
In this disease, the body is essentially allergic to the TH. Hence, the immune system forms antibodies, which mistakenly attack its own thyroid gland tissues, destroying the gland's ability to secrete hormones. The most common form of such autoimmune disorder is Hashimoto's Thyroiditis.
Other factors hypothesized to cause malfunction of the thyroid gland include: viral/bacterial/Candida infections, pregnancy, trauma, poor diet, radiation from X-rays, alcohol and drugs, toxins especially those created from petrochemicals. 
Many plastics, pesticides, fertilizers, dioxin, body care products etc., contain xenoestrogens (substances that mimic estrogen in our body) which disrupt our endocrine system and therefore, hormonal imbalance. In addition, chronic stress could result in fatigue in our Adrenal glands, interfering with the conversion of T4 to T3 (3).
To offer you a different angle on this matter, eastern medicine believes thyroid disorders to be symptoms of a Heart-Mind connection that is out of sync, a disharmony in yin-yang and blood of the heart.  Another possible cause could be an imbalance in one's kidneys (9). 
The Role of Estrogen in Regulation and Function of the Thyroid.
Thyroid diseases have been known to strike more women than men (Note: Men are not impervious to the disease, just statistically less occurrences relative to women), especially in the period between puberty and menopause, most probably due to the secretion of the hormone Estrogen. Not only are women are more susceptible to disorders related to iodine deficiencies, they are also three times more prone than men, to have cancers pertaining to the thyroid gland (4).
Previous studies have shown the effect that estrogen plays on thyroid efficiency, via its role on T4 binding globulin (a carrier for T4 in our blood stream). However, more recent works have suggested that estrogen also directly affects thyroid function and its growth. Details of this mechanism is summarized in the next paragraph.
Estrogen signaling occurs when the hormone estrogen bonds with its Receptors. Therefore, the presence of estrogen receptors (ER), namely ER alpha and ER beta, is absolutely essential in any direct estrogenic action. It has been discovered that thyroid tissue expresses both ERs. It is also very interesting to note that the binding action between estrogen and its ERs in Thyroid tissue have different effects on the growth of Thyroid cancers: (i) Bondage to ER alpha increases proliferation of cancer cells while (ii) Bondage to ER beta suppresses growth of such tumors.
Iodine's Role in Thyroid Disease
Iodine's role on the health our thyroids requires little introduction. However, lesser is known of its actual effects. Iodine is essential in the formation of TH. Post absorption from our intestines, iodine turns into iodide in our blood, which in turn integrates with another substance, the amino acid Tyrosine, to eventually form TH. A deficiency in iodine will therefore lead to an underproduction of TH (6).
At the same time, lack of iodine also causes Goiter (an enlargement of thyroid gland). It is estimated that about 200 million people worldwide suffers from Goiter (an enlarged thyroid gland) to some degree, and that most of these cases are caused by a deficiency in iodine. 
On the other hand, it is important to note that a diet that is excessive in iodine intake could also cause toxicity and complications of the thyroid such as Thyroiditis (an inflammation of the thyroid gland).
Selenium's Role in Thyroid Function
Another mineral closely linked to thyroid is Selenium. Although less have been heard on this front, it is gaining more attention as recent research confirmed that thyroid tissue comprises more selenium than any other body tissue (7).
Some diseases affecting the thyroid, such as Grave's (a condition marked by over activity in the thyroid a.k.a. Hyperthyroidism, "hyper" meaning "over"), as well as hypothyroidism, have been associated with selenium due to the mineral's impact on the conversion of T4 to T3. In addition, Cretinism (marked by stunted physical and mental growth due to congenital hypothyroidism) is yet another condition that has been linked to combined deficiencies in both selenium and iodine. 
However, studies do not show selenium intake to have any effect on thyroid autoimmunity (cases where the immune system attacks the body's own thyroid gland). Moreover, overdosing on selenium could cause Selenosis (selenium toxicity), which is characterized by diarrhea, fatigue, hair loss and possibly fingernail discoloration.
The Role of some Vitamins in Thyroid Disorders
Some evidence surfaced to show positive effects of vitamins with antioxidant properties on thyroid diseases, while supplementation of vitamin D also appeared to benefit the patients’ skeletal systems. Vitamins B6 as well as B12 have also been shown to play a part in conjunction with disorders of thyroid function. However, there is no information to prove the efficacy of vitamin supplementation in the prevention of thyroid cancers (8). 
Vitamins A, C, E.
This group of vitamins posses antioxidant properties i.e. they limit the damage caused by oxidative byproducts (free radicals) in our bodies as a result of normal metabolism. First, both hyper and hypothyroidism elevate cellular oxidation by intensifying the reactivity of oxygen molecules in the body. Second, both forms of thyroid malfunction exacerbate the problem by decreasing levels of antioxidant vitamins in our bodies, further hampering their abilities to counter free radicals.
So far, research has shown that administration of vitamin E to benefit individuals with either hyper or hypothyroidism. At the same time, treatment with vitamin C, E, beta carotene, selenium, zinc and copper, did reduce symptoms in patients with hyperthyroidism. 
Vitamin A
In animal studies, vitamin A, on its own, appeared to be closely-knitted with the mechanisms of the hypothalamic-pituitary-thyroid triangle described above. When the human body is lacking in vitamin A, thyroid cells' uptake of iodine is reduced, thus depressing TH production and output.
Vitamin B6
A vital co-enzyme for over 100 enzymatic reaction in our bodies, this vitamin also affects communication between the hypothalamus, pituitary and thyroid glands. Contradictory as it sounds, studies have shown that a deficiency in B6 causes hypothyroidism due to reduced hypothalamic expression of TRH, while overconsumption of the same vitamin would result in low levels of TSH from the pituitary gland. 
Vitamin B12
At this point, various studies have shown a relationship between vitamin B12 deficiency in cases of thyroid diseases, particularly in those individuals with autoimmune thyroid disorders. However, it is important to note that where such vitamin deficiency occurs, Gastrin levels (gastrin is a hormone which stimulates secretion of gastric acid) should also be examined at the same time, as fluctuating levels of gastrin might be the cause of B12 malabsorption and thus, low B12 concentration levels in the blood.
Conclusion
As you can appreciate by now, the physiology of thyroid functions and causes of thyroid diseases are complex and intricate. Diagnosis of the disorder could also be difficult and less obvious because of the common symptoms shared with other diseases. But, a disordered thyroid that is left untreated could lead to other health complications including osteoporosis, obesity, hypertension and heart disease (that would be a whole different discussion).
Nutrition and supplementation could possibly be beneficial in cases of deficiency but that has to be determined in each scenario. Clearly, prudence and moderation is the key here and always. Over supplementation would be pointless and wasteful at best; and in the worst case, could become toxic to our bodies. 
If you are already on medication to treat an existing thyroid disorder, do bear in mind that chemicals, drugs and supplementation (yes, even natural herbal ones) will interact and react with each other. It would be wise to check with your health care provider before you embark on a course to ensure your safety.
References:
  1. American Thyroid Association (2003), ATA Hypothyroidism Booklet, retrieved Feb 14, 2012 at www.thyroid.org.
  2. Kostoglou-Athanassiou I, Ntalles K (2010), Hypothyroidism - new aspects of an old disease, Hippokratia 2010, 14, 2: 82-87
  3. Friedlander Jodi, Bauman Edward (2007), Hashimoto's Autoimmune Thyroiditis: Eating for Health, Applications for Recovery, Bauman College Holistic Nutrition ans Culinary Arts, Pp 2-4
  4. Santin Ana Paula, Furlanetto Tania Weber (February, 2011), Role of Estrogen in Thyroid Function and Growth Regulation, Journal of Thyroid Research, Vol 2011, Article ID 875125, doi: 10.4061/2011/875125
  5. Melish John S., Clinical Methods: The History, Physical and Clinical Examinations, 3rd Edition (1990), Chapter 135: Thyroid Disease, Boston: Butterworth.
  6. Hamwi George J., Tzagournis Manuel, Nutrition and Diseases of the Endocrine Glands, The American Journal of Clinical Nutrition, March 1970, Vol 23, No.3, Pp.311-329.
  7. Duntas Leonidas H., Selenium and the Thyroid: A Close-Knit Connection, Journal of Clinical Endocrinology Metabolism, December 2010, 95(12):5180-5188
  8. Sworczak Krzysztof, Wisniewski Piotr, The Role of Vitamins in the Prevention and Treatment of Thyroid Disorders, Polish Journal of Endocrinology, Volume 62, Number 4/201, Pp 340-343
  9. Pitchford Paul, (2002), Healing with Whole Foods, Asian Traditions and Modern Nutrition, 3rd Edition, Pp, 333, North Atlantic Books, Berkeley, California.

3 comments:

  1. Thanks for the detailed description.

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  2. Would you suggest some natural remedies?

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  3. My thyroglobin is 145 what can I use

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