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The functions of the thyroid gland are complex but its regulation is easy to understand…

The thyroid gland produces hormones (T4 and T3) which pass into the blood and act on the different “target” organs allowing them to function correctly (the heart, muscles, brain).

Thyroid hormones control metabolism (i.e. the proper use of energy) which also helps keep the body at the right temperature.

The thyroid gland is itself controlled by a hormone produced by the pituitary gland: TSH (Thyroid Stimulating Hormone).

The pituitary gland has sensors that are extremely sensitive to the T4 level in the blood and will therefore very precisely adapt the production of hormones by the thyroid gland.

A normal TSH therefore means  that the thyroid gland is functioning well; we speak of euthyroidism.

In contrast, if the production of hormones is too high, we will have a low TSH and we speak of hyperthyroidism.

On the other hand, if the gland does not function sufficiently, it will be hyperstimulated by the pituitary gland with a high TSH; It's hypothyroidism.  


Published in “Le Parisien” on August 23, 2017

Thyroid hormones regulation

To watch the film: “How the thyroid works” produced by the company Medtronic, click on the link:                                


We speak of hyperthyroidism when there are too many hormones in the body which leads to an acceleration of all functions; often the patient will say that he feels "speed". The main symptoms are: nervousness, irritability, fatigue, sleep problems, diarrhea, tremors, sweating. Muscle weakness and palpitations are very common signs; weight loss is seen in intense forms.

The onset of hyperthyroidism can be quite sudden, especially in Graves' disease and is sometimes accompanied by eye problems (exophthalmos) and goiter (enlarged thyroid gland volume).

The blood test will find a collapsed TSH and T4 and T3 hormones more or less high depending on the intensity of the hyperthyroidism.



We speak of hypothyroidism when there is a lack of hormone in the body and this will result in numerous symptoms which are the result of a slowdown in metabolism (fatigue, apathy, weight gain, chilliness, constipation, hair loss, etc.). The onset of hypothyroidism is generally very gradual and this pathology can therefore be overlooked. The diagnosis is made by blood tests. Initially there is an isolated elevation of TSH with circulating hormones at the lower limit of normality. At the stage of frank hypothyroidism, circulating hormone levels (T3 and T4) are low.

The main cause of acquired hypothyroidism in adults is Hashimoto's disease, which corresponds to chronic inflammation (thyroiditis) caused by an abnormal reaction of the immune system which "attacks" the normal gland (auto-disease). immune). Hashimoto's disease is very often familial. The diagnosis is made when we find an elevation   anti-TPO antibodies in the blood. Hashimoto's disease may be associated with benign nodules and thyroid cancers.

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