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Thyroid Disease



We hear so much about thyroid glands and hormones in this era of obesity.  When someone is overweight, and seems to have a “low metabolism” it’s chalked up to having low thyroid hormones.  We also realize that many hormone disruptors interfere with thyroid hormone manufacturing and utilization in our bodies.  So what is thyroid hormone?  Where does it come from? What does it do?


The thyroid gland is a small butterfly shaped endocrine gland situated in the low part on the front of the neck.  It is responsible for synthesizing thyroid hormone.  The endocrine system is very complicated and when working normally, precise.  Very small amount of hormone can have a huge impact of various organs and tissues far removed from its production sites.  Thyroid hormone is no exception.



Why Is Thyroid Hormone So Important?


Thyroid hormone is responsible for converting calories and oxygen into energy for the cells to use.  Every cell requires energy in order to perform its unique duties.  This conversion of calories into energy is called metabolism.  So, thyroid hormone is necessary for cell metabolism.


The developing brain cells of fetuses require thyroid hormone to mature.   Thyroid hormone helps to regulate long bone growth and helps the body respond to *other* hormones better.  Thyroid hormone stimulates heat production (as mentioned earlier).


Increased energy utilization results in less energy (i.e. fat) storage.  If you use it, you lose it.  Thyroid hormones helps our bodies *use* the energy we ingest.  There are also studies that suggest that thyroid hormone  directly targets human hair follicles whereby thyroid hormone causes a proliferation, and a decrease in death, of hair matrix keratinocytes (affecting the hair color).  Thyroid hormone also prolongs the growing phase (anagen) of the hair growth cycle – resulting in longer, thicker hair.




Thyroid Gland and the Feedback Loop

(hypothalamus-pituitary-thyroid feedback axis)


The purpose of the thyroid gland is to synthesize thyroid hormone (T3 and T4) and calcitonin.  Thyroid hormone is primarily used to mediate cell metabolism.   T3 is the more potent version of thyroid hormone and is produced in smaller quantities (20%).  T4 is less potent, more plentiful, but undergoes conversion to T3 when additional thyroid hormone effect is needed by the body.


Thyroid hormone is produced in the thyroid gland and requires iodine and tyrosine.  Thyroid hormone is carried around in the blood by binding proteins. A very small amount is “free” or unbound.  Only the free hormone that is active.


Thyroid Gland

The production, storage, and conversion of inactive hormone to active hormone are mediated by a complex feedback loop involving the hypothalamus and the pituitary gland.


When the thyroid hormone level in our body is too low, the hypothalamus produces TRH (TSH releasing hormone).  This TRH signals the anterior (front) pituitary gland to produce thyroid stimulating hormone (TSH).  Thyroid stimulating hormone moves through the blood to the thyroid gland, and *stimulates* the gland to release T3 and T4.


When the T3 and T4 levels increase to a nice comfortable level for the body, the pituitary senses the higher levels of T3 and T4, and stops secreting TSH.  So this stops the stimulation of the thyroid gland to release additional hormone.


The hypothalamus tells the pituitary when the thyroid hormone level is “right.”Since thyroid hormone regulates energy utilization by the cells, in situations when the body needs the capacity to convert more calories to energy, like in cold environments when energy is needed to create body heat, the hypothalamus will release TRH.  TRH then stimulates the pituitary gland, to stimulate the thyroid gland, to produce thyroid hormone, to allow the muscle cells to shiver to create body heat.  Complicated!





Hypothyroidsim


Thyroid hormone deficiency results from:


Problems with the hypothalamus-pituitary-thyroid axis; either acquired or congenital (from birth)


Problems with the thyroid gland itself – possibly due to disease, radiation, surgery, radiation thyroid treatments, and some viruses can cause problems with thyroid gland function


Lack of substrate to make the hormone – like iodide deficiency


Some medications and drugs


Sex hormones blunt the effects of thyroid hormone – so estrogen dominance contributes to thyroid hormone dysfunction


Therefore exogenous estrogen sources interfere with proper thyroid function.



Problems That Result From Thyroid Deficiency:


  • Obesity
  • Brittle, short hair and nails that fail to grow
  • Lack of energy – fatigue
  • Depression
  • Cold intolerance
  • Heart failure
  • Constipation
  • Skin changes
  • Diminished taste, smell
  • Thinning eyebrows
  • Coma and death can result.  (myxedema coma)



Diagnosis and Treatment:


There are various laboratory tests that can be done to begin an investigation into thyroid function.  The most common and readily available are TSH, T3 and T4.  Typically the TSH becomes abnormally elevated as it tries to stimulate the thyroid gland to crank out more hormone when the levels are a bit low.  When the level doesn’t rise as expected (due to thyroid gland dysfunction) the pituitary squirts out even more TSH.  So TSH level is a sensitive indicator of thyroid gland dysfunction – abnormal even before the hormone levels are low in some cases.  And if the levels are not very low, then there are no noticeable symptoms.


T3 and T4 measure the amount of hormone in the blood.  Most of it is bound to protein, so there are also protein binding tests that can be done.  By measuring a multitude of hormone levels in this way, we can tell if it’s the pituitary gland, hypothalamus, the thyroid gland, or the hormone with the problem.  After the problem has been identified, we can move on to finding a solution.



Maintain A Healthy Thyroid By:


Avoiding estrogenic substances in your life.Organic foods, meats without added hormones, non-toxic cleaning products, and avoiding hormone disruptors.


Eat a balanced diet so you ingest adequate vitamins and iodine.


Periodically have your thyroid function tests evaluated – especially if you are (or plan to become) pregnant.  Thyroid hormone is critical in brain development in fetuses, and you don’t want to be deficient.  And it’s probably a good idea to have the newborn’s thyroid levels evaluated.


If you require extra thyroid hormone (because your own is too low), be sure to take the medication.  You will do yourself no favors if you are non-compliant with this particular medication for the reasons listed above.  We do not recommend ingesting “natural” thyroid supplements.  The potency and doses will vary in these formulations (and the ratio of T3/T4 may be incorrect), so it is difficult to know exactly what you’re taking.  And the thyroid hormone is MUCH too important and critical to be unsure.  Levothyroxine is the most commonly prescribed thyroid replacement hormone formulation, and if you have hypothyroidism, will likely be what your physician prescribes.