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.
References
Awad AG. (2000).
The thyroid and the mind emotions/thyroid disfunction and mental disorders. Thyrobulletin.
Musselman DL and
Nemeroff CB. (1996). Depression and endocrine disorders: Focus on the thyroid
and adrenal system. British Journal of
Psychiatry.
Engum A et al.
(2002). An association between depression, anxiety and thyroid function – a clinical
fact or an artefact? Acta Psychiatrica
Scandinavica.
Kirkegaard C and
Faber J. (1998). The role of thyroid hormones in depression. European Journal of Endocrinology.
Underactive
thyroid. NHS Choices. http://www.nhs.uk/conditions/Thyroid-under-active/Pages/Introduction.aspx
