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Thyroid hormone physiology primer
Many of you come to my office with a complaint of hypothyroidism, only to be told by your primary care physician that testing is normal. Guess what? You are correct!! But you too. However, you haven't gone far enough to document what you believe to be true. Your thyroid produces adequate amounts of thyroid most of the time. After it leaves the gland, the brain takes control and responds to environmental influences, sleep, stress, exercise, etc. This response changes the activity of enzymes that control the conversion of your thyroid hormone into its more active form, called...
Thyroid hormone physiology primer
Many of you come to my office with a complaint of hypothyroidism, only to be told by your primary care physician that testing is normal. Guess what? You are correct!! But you too. However, you haven't gone far enough to document what you believe to be true. Your thyroid produces adequate amounts of thyroid most of the time. After it leaves the gland, the brain takes control and responds to environmental influences, sleep, stress, exercise, etc. This response changes the activity of enzymes that control the conversion of your thyroid hormone into its more active form, known as T3. This needs to be assessed to adequately determine your true thyroid activity. I have included a feedback table of this physiology below.
The following is a thyroid axis review:
HYPOTHALAMUS->TRH(Thyrotropin releasing hormone - this is reduced in times of stress) ->PITUITARY———>TSH(Thyroid stimulating hormone – also decreased during times of stress) ->THYROID(The gland produces 4 types of thyroid hormone,T1-4– 90% of the performance asT410% of the performance asT3.T2 and T1are <1% of performance).
T3is 5 times stronger thanT4. As such 50-80% ofT4is converted to its stronger counterpart,T3. The conversion occurs through the activity of enzymes called DEIODINASES. They are known as theD1-3Enzymes. This is how the brain controls thyroid activity and why during times of stress thyroid activity is reduced.
D1 and D2Control the transformation into muscle and nerve. However, when stress occurs, the conversion of the D3 enzyme is activatedT4->rT3-reverseT3.Reverse T3is unable to bind the thyroid receptor and acts as a “thyroid brake” limiting the metabolic actions of the thyroid.
The primary stress hormone that controls all of this isCRH(Corticotropin releasing hormone). This is also released by the hypothalamus in the brain. It stimulates the release ofACTH(adrenocorticotropin hormone). It stimulates the adrenal gland to release adrenaline and cortisone, the primary stress hormones. When CRH is released,TRHand consequentlyTSHare reduced. Think about it this way. The main function of the thyroid is to adjust the metabolic rate and oxygen consumption in the body. When the thyroid is reduced, fatigue, drop in body temperature, weight management problems, constipation, hair loss, etc. occur. This happens under stress because the brain feels it needs to prioritize tanking to deliver the stress response, which may include running or fighting to escape danger. Reducing metabolic rate by reducing thyroid activity helps the body obtain adequate fuel for the stress response/escape. When your primary care doctors assess your thyroid, they generally just take measurementsTSHand maybeT4. They don't look at the rest of the chemistry.
When they tell you that your thyroid is producing normally, they are technically correct, but they do not take into account the environmental influences that we all endure these days. Not to mention, there are micronutrient problems/deficiencies in our food supply that deny us adequate micronutrient support that supports normal thyroid conversion. Without judgingT3andrT3There is no recognition of environmental/nutritional problems and the cause of hypothyroid symptoms may be overlooked. But here it isKEY POINT!When your brain doesn't allow conversionT3and maneuveringrT3Instead, this is done to compensate for your lifestyle and stressors to keep you safe. In many cases trying to deliverT3To compensate for an altered conversion, the problem is not solved because the brain sees this as a violation of its programming. In my experience, most of the time some improvement can be achieved from this chemistry. However, you may not be able to regain full balance without paying homage to your stressors. Sorry, this is just the reality of how this works. This is a very complex chemistry that requires more thorough evaluation when symptoms of low activity are present. More and more doctors are looking into this in more detail. Hopefully this primer will enlighten you a little about what to look for and ask your doctor about. Unfortunately, you may not receive a positive response to your request. Be brave, there are more of us out there who will listen.
Hope this helps…..
Inspired by Courtney P Ridley