What is the thyroid gland?
The endocrine system is responsible all hormone production, and therefore all of functions that hormones regulate in the body. The endocrine system includes the hypothalamus, pituitary gland, pineal gland, adrenal gland, pancreas, ovaries/testes, parathyroid gland and thyroid gland. The thyroid gland is at the base of the neck and is split into two lobes, one located on either side of the windpipe. It is responsible for producing three hormones that are important for regulating many metabolic processes in the body.
The main hormones produced by the thyroid gland are calcitonin, T3 (tri-iodothyrionine) and T4 (thyroxine). Calcitonin is involved in controlling the tightly regulated calcium levels in the blood.
It is involved in a negative feedback loop with parathyroid hormone. T3 and T4 help to regulate the body’s metabolism and are the hormones that are involved in common thyroid diseases.
Types of thyroid disorders
Hyperthyroidism is when the thyroid is overactive and produces too many hormones. This causes the body’s metabolism to speed up and use energy faster than it should. Symptoms can include an enlarged thyroid gland, anxiety, nervousness, restlessness, irritability, weight loss and sleep disturbances.
Hypothyroidism is when the thyroid is underactive and does not produce enough hormones. This causes the body’s metabolism to slow down and use energy at a slower pace. Symptoms can include fatigue, difficulty concentrating, loss of interest, memory difficulties, weight gain and mood swings. Some of these symptoms are also indicators of depression.
Both hyperthyroidism and hypothyroidism can be caused by various conditions and factors. Thyroid disorders can be diagnosed through a blood test measuring T3, T4 and thyroid stimulating hormone (TSH).
Thyroid gland and depression
It has been found that depression may be a symptom of hypothyroidism. There are various postulated theories which involve the following neuro-endocrine communication path - the thyroid gland receives a signal from the hypothalamus in the brain when T3 and T4 need to be produced. The messenger delivering this signal is thyrotropin-releasing hormone (TRH), which signals the pituitary gland to produce thyroid-stimulating hormone (TSH), then telling the thyroid gland to secrete T3 and T4 to the body. Once the correct levels are reached in the blood, the thyroid gland is signalled to stop producing T3 and T4. Patients with major hypothyroidism and depression tend to have an abnormality in the communication between TRH and TSH.
As depression is multifactorial and can be cause by a range of both internal and external stressors, it is important to have a diagnostic blood test done do ensure thyroid levels are normal. Sometimes thyroid conditions can be overlooked and patients may be prescribed anti-depressants when in fact thyroid hormone tablets are required.
In conclusion, the cause of the psychological symptoms associated with the thyroid gland are often related to abnormal thyroid hormone levels. The goal for treating any thyroid disorder is to restore normal blood levels of the thyroid hormones. Hypothyroidism is commonly treated by taking hormone replacement tablets, though it may take time and regular blood tests to identify the correct replacement dosage. Hyperthyroidism is a bit more difficult to treat as it requires the blocking of hormone production.
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