June 10, 2022


To address a health problem accurately, it is essential to have a correct diagnosis. Otherwise, the treatment will be ineffective or, worse still, we will go around blindly without solving anything.

Unfortunately, academic medicine is very gridlocked and anything that slightly falls outside the diagnostic criteria is either not evaluated or is classified as a “functional” disorder and the causes are not further investigated to find the best solution.

This happens in many aspects, one of them is the thyroid and its imbalances. And a thyroid imbalance can cause many symptoms that are often ambiguous such as fatigue, hair loss, low mood, brain fog...

If it is detected that the thyroid is failing, the patient will probably receive hormone replacement treatment, but that is not always the solution, because it is not taking into account that the production, conversion and absorption of thyroid hormone in the body involves several steps and that a malfunction can occur in any of them. For this reason, there are patients who manage to regulate their laboratory parameters but continue to feel unwell.

If we add to this that, in some cases, Laboratory tests may be normal, it could happen that the doctor directly rules out that the person is suffering from thyroid problems, so they will not have access to adequate treatment. 

Normally the doctor will only ask, first, the TSH and T4 values ​​(without taking into account other aspects such as T3 or antibodies). Furthermore, lab ranges are not based on research that tells us what a healthy range might be, but on the average of values ​​obtained from people who come to labs for testing, which includes people whose health is not optimal (in "Gray zone").

The idea of ​​this post is to mention the patterns of thyroid alteration that often go unnoticed.

1. Insufficient conversion of T4 to T3

The thyroid gland makes two hormones: approximately 75% is T4 and 25% is T3. T4 is the inactive form and must be converted to T3 for the body to use.

There are certain aspects that block the transition from T4 to T3, the most common being chronic low-grade inflammation and excess stress hormones. In both cases the brain interprets that “it must save energy” and that is why it blocks the conversion. 

With this pattern you will have symptoms of hypothyroidism, but your TSH and T4 will be normal. Here it may be interesting to ask for total T3, free T3 and reverse T3, but the key will be to determine, with the clinical interview, if there is inflammation and/or stress.

2. Alteration of the hypothalamic-pituitary/pituitary-thyroid axis

Imagine a factory. The boss is the hypothalamus, in the brain. Below it we have the pituitary gland, the one in charge that receives orders from the boss and transmits them to the workers. And in this case, the workers are the thyroid gland. Logically, if communication fails, the assembly line breaks down.

The boss communicates with the manager through the hormone TRH (thyrotropin-releasing hormone) and the one in charge with workers through TSH (thyrotropin or thyroid-stimulating hormone).

When the boss detects something that stresses him: psycho-emotional stress, an active infection, significant intestinal dysbiosis, resistance to the hormone insulin or even during pregnancy, he reduces the production of TRH, which will in turn reduce the production of TRH by the pituitary gland. TSH and the workers will stop receiving orders, lowering the production of T3 and T4.

Here we normally find TSH and T4 levels falling (although they could still be within the normal range) 

3. Thyroid resistance

We talk about resistance to a hormone when, even though hormone levels may be correct, the hormones do not reach the cells where they are needed, causing symptoms of hypothyroidism.

Logically, here we can have all the laboratory standards within normal ranges, because that is not where the problem lies. Today there is no way to know with an analysis whether the cellular hormone receptors work correctly or not.

It is speculated that the cause of this resistance may be stress, elevated homocysteine ​​levels and even genetic factors. At the genetic level we cannot do much, but we can work on the other two axes, greatly improving the patient's quality of life.

As said at the beginning of the article, the key to success is a good diagnosis. Laboratory tests are complementary, but what matters is a good interview to assess the patient's context. This is what will allow us to develop the best action plan individually.

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