In Newsletter9, we have seen that a selenium deficiency triggers hypothyroidism.

The symptoms of hypothyroidism by selenium deficiency do not differ from the symptoms of hypothyroidism caused by an insufficient thyroid hormone production by the thyroid gland.

Here Is Why

In both cases the cells that rely on thyroid hormone for the regulation of their activity, are deprived of sufficient thyroid hormone. Hence identical symptoms appear.

In case of hypothyroidism by thyroid gland insufficiency, the origin of the symptoms is obvious. There is lack of thyroid hormone in circulation. Blood tests will indicate it. Also the TSH test--a test that monitors the thyroid gland's ability to produce thyroid hormone--confirms that the thyroid gland is unable to deliver a sufficient quantity of thyroid hormone in the blood circulation.

In case of hypothyroidism by selenium deficiency, the symptoms are the same, only their origin is less obvious.

The blood tests indicate that thyroid hormone is present in the circulation in acceptable quantity.
There are two thyroid hormones in circulating blood : Tetraiodothyronine (T4) and triiodothyronine (T3). T3 is about 15 times stronger than T4. As we have seen in Newsletter9 , Selenium is essential for the conversion of T4 in T3.
In case of hypothyroidism by selenium deficiency, subtle differences may occur in the thyroid hormone blood test results, like a relatively lower level of T3 and an unbalance in the T4 to T3 ratio. These subtleties are easily overlooked, because in the case of hypothyroidism by selenium deficiency, the TSH test indicates that the thyroid gland produces sufficient thyroid hormones to maintain the thyroid hormone blood levels between acceptable range.

Subtleties

For those interested in endocrinology, I like to demonstrate how the situation can become more complicated :

In case of hypothyroidism by selenium deficiency, the task of the thyroid gland to maintain thyroid hormone blood levels is greatly facilitated by the fact that the thyroid hormone in circulation is less utilized.
In such case, the TSH test will fail to detect a possible to small or inefficient thyroid gland.

Should the selenium deficiency recede and the thyroid hormone in circulation become utilized by the cells, the possible to small or inefficient thyroid gland may now become unable to maintain the thyroid hormone blood levels.

Symptoms of hypothyroidism will reappear, this time caused by a thyroid gland deficiency.

Conclusion

The elucidation of the origin of a hypothyroidism has always be a complicated task for physicians.

Before the discovery of the role of selenium in the metabolism of thyroid hormone, many cases of hypothyroidism went undocumented and untreated because of a discrepancy between the symptomatology of hypothyroidism and the blood test results whenever the condition is not directly related to an underfunction of the thyroid gland.