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The endocrine system is made up of glands that produce and secrete hormones. These hormones regulate the body’s growth, metabolism and sexual function.
The endocrine system includes the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal gland, and the reproductive organs (ovaries and testes). The pancreas is also a part of this system; it has a role in hormone production as well as in digestion.
The Thyroid in The Endocrine System
The hypothalamus sends a signal to the pituitary gland, which stimulates the pituitary to secrete TSH. This TSH then tells the thyroid gland to secrete hormones, such as T3 and T4.
So imagine it like this:
Hypothalamus (sends signal to) > Pituitary (sends signal to) > Thyroid
So, the hypothalamus and the pituitary gland work to ensure the thyroid functions correctly, releasing the hormones (T3 and T4) and the amounts of them that we need, in order to feel well. However, having hypothyroidism, this doesn’t always happen. A problem can be that the hypothalamus, the pituitary or the thyroid itself not doing its job in this sequence.
In primary hypothyroidism, your thyroid is being stimulated properly, but it isn’t producing enough thyroid hormones (T3 and T4). This means that the thyroid itself is the source of the problem. This is what most of us with hypothyroidism have.
In secondary hypothyroidism, the pituitary gland or hypothalamus isn’t stimulating the thyroid to produce enough hormones. In other words, the problem isn’t with the thyroid, but the pituitary or hypothalamus. This is much less common. An example is hypopituitarism.
Primary hypothyroidism is the most common type of hypothyroidism, with the autoimmune disease Hashimoto’s Thyroiditis being the main cause (at around 90%) of primary hypothyroidism cases. Both secondary and primary hypothyroidism are usually treated using thyroid hormone replacement medication.
The adrenal glands are also part of the endocrine system, so it’s understandable that when thyroid function goes wrong, i.e. is under attack from Hashimoto’s and not properly managed, that the adrenal glands can also feel the strain.
When the body is under stress, the adrenals usually act by producing extra cortisol to keep us going. However, the they can only keep this up for so long, before they are thought to dysfunction, leading to adrenal fatigue (though it is more accurately referred to as hypothalamic-pituitary axis dysfunction). This can be in the form of high, low or combined high and low cortisol. In Thyroid Pharmacist Izabella Wentz’s experience, adrenal dysfunction is present in 90% of those with autoimmune hypothyroidism. 
Adrenal fatigue symptoms include tiredness, sleep disturbances, heat intolerance, sweats/flushes, weight gain especially around the stomach, anxiety, changes to personality and feeling irritable, with a ‘normal’ or low TSH readings and a high Free T3 level.
The thyroid and adrenals work together to keep many bodily functions and processes working correctly, so we feel and function well. They’re both part of the endocrine system, and when treating hypothyroidism, we need to keep in mind that we also need to work on keeping the whole endocrine system healthy to support good thyroid and adrenal health.
Sex hormone imbalances (involving the ovaries for example) can also occur with other endocrine issues. In my personal experience, poor gut health was driving adrenal dysfunction, which then lead to oestrogen dominance. Each part of the endocrine system can have a knock on effect to another.
If you have adrenal issues, you will need to correct them in order for your thyroid medication to work to its full potential, and if you have thyroid problems, you need to ensure that it is managed properly to minimise stress done to the adrenals.
Did you know how the different parts of the endocrine system worked with one another?
You can click on the hyperlinks in the above post to learn more and see references to information given.
Further reading: Adrenal Fatigue by James Wilson