It is located in the neck and secretes the thyroid hormones thyroxine (T4) and triiodothyronine (T3).
These are essential for normal growth, they control the basal metabolic rate and the metabolism of all body tissues.
They also play an important role in the metabolism of proteins, carbohydrates and lipids. An example of this is the increase in cholesterol levels in patients with hypothyroidism .
In order for the thyroid to secrete these hormones, it needs to be stimulated. The pituitary gland (responsible for the secretion of this hormone) is under the control of another section of the brain, the hypothalamus , where another hormone, the thyroid-releasing hormone (TRH), is secreted.
HRT stimulates the secretion of TSH. TSH travels from the pituitary gland through the bloodstream to the thyroid, where it stimulates the secretion of hormones T4 and T3.
If the patient’s thyroid produces excess thyroid hormone ( hyperthyroidism or thyrotoxicosis ), the TSH level is suppressed. Conversely, if the patient’s thyroid produces too little thyroid hormone (hypothyroidism), TSH levels increase in an attempt to try to stimulate the gland to secrete the hormone responsible.
TSH is very sensitive to thyroid disorders and can be used alone as a first-line thyroid function test. If it is normal, the thyroid function can be considered normal and, if not, it is determined that T4 or T3 diagnose the anomaly.
This is a disorder due to the decrease in the functioning of the thyroid gland . This is due to disorders of the thyroid gland ( primary hypothyroidism ) due to disorders of the pituitary gland (secondary hypothyroidism).
This disorder usually develops slowly, and due to its non-specific symptoms it is often overlooked or misdiagnosed as depression .
Common symptoms include:
- Lethargy / fatigue.
- Intolerance to the cold.
- Weight gain.
- Dry skin and hair.
- Constipation .
Hypothyroidism is common in the elderly. It is easily treated by means of therapy. TSH can be used to diagnose hypothyroidism and also to monitor compliance in patients treated with Eltroxin.
Congenital hypothyroidism ( cretinism ), which occurs from birth, is a relatively common disorder and is treatable. However, if the diagnosis is missed, it can cause growth and mental retardation in the affected child. For this reason, all newborns are evaluated with a TSH measurement.
This is mainly due to a thyroid gland with hyperactivity (primary hyperthyroidism), but also, it may be due to overtreatment with Eltroxin. In very rare cases, it is due to hypersecretion of TSH by the pituitary gland.
Common symptoms include:
- Weight loss despite a normal appetite.
- Sweating / heat intolerance.
- Agitation / tremors.
- Generalized muscle weakness.
- Menstrual abnormalities.
- Goiter (swelling of the front of the neck).
TSH can be used to diagnose hyperthyroidism, since elevated thyroid hormones will suppress TSH secretion from the pituitary gland.
Why is TSH measured?
- Increase in primary hypothyroidism (underactive thyroid gland).
- Decrease in secondary hypothyroidism (problem in the pituitary gland).
- Decrease / suppression in primary hyperthyroidism (hypoactive thyroid gland).
- Increase in secondary hypothyroidism (problem in the pituitary gland).
- To be used for the follow-up of patients with Eltroxin.
- To control the dose and verify compliance.
How should I prepare?
A blood sample is taken at random for TSH determination. No specific preparation is needed, and if you are taking Eltroxin, continue with regular intake.
How is the procedure performed?
A small amount of blood is removed from your arm and taken to the laboratory for analysis. Apart from a small amount of discomfort, there are no risks involved.
It may bleed slightly after the procedure, but if pressure is applied in the area, this is unlikely. You may have a slight bruise in the area if your veins are hard to find.
What are the restrictions of the procedure?
Certain medications can affect thyroid function tests. Some examples are lithium (used to treat certain psychiatric disorders), amiodarone (used to treat abnormal heart rhythms), certain anticonvulsants, heparin (decreases the likelihood of blood clots) and aspirin.
In systemic disease, the normal regulation of T4, T3 and TSH is altered. TSH can decrease with low levels of T4 and T3 without evidence of thyroid disorder. This is corrected once the patient recovers and is known as “non-thyroid disease”.
Clinical definition of thyroid stimulating hormone (TSH)
The TSH test checks the amount of thyroid stimulating hormone (TSH) in the blood to diagnose thyroid disorders and identify the treatment of hypothyroidism and hyperthyroidism. TSH is produced by the pituitary gland and regulates the release of thyroxine (T4) and triiodothyronine (T3) hormones.
The thyroid is a small butterfly-shaped gland located in the lower part of the neck. It is an endocrine gland that synthesizes hormones. Thyroid hormones help regulate metabolism and control the speed of many metabolic activities in the body.
The thyroid profile tests verify the functioning of the thyroid and are also used to diagnose thyroid diseases such as hyperthyroidism and hypothyroidism. Thyroid profile tests include a blood test that involves drawing blood from the body for testing in a pathology laboratory.
The thyroid blood test includes:
- A TSH test to measure the level of the thyroid stimulating hormone in the blood. It is used to measure thyroid activity in the body.
- The T4 test is a thyroxine test. A high level of hormone T4 indicates an overactive thyroid (hyperthyroidism).
- The T3 test verifies triiodothyronine hormone levels. This test is done if the T4 and TSH tests suggest hyperthyroidism. The T3 test can also be performed if there are signs of an overactive thyroid gland.
How long are the results?
- From 24 to 36 hours.
Why do the test?
The TSH test is performed to verify thyroid function and / or symptoms of hyper or hypothyroidism. The TSH test aims to:
- Diagnose a thyroid disorder in a person with indicative symptoms.
- Adults with any thyroid disorder.
- Newborns with underactive thyroid.
- Verify thyroid replacement therapy in people with hypothyroidism.
- Identify and detect problems of female infertility.
- It controls the functioning of the pituitary gland when necessary.
If you have any of the following conditions, a test for thyroid disorders should be done:
- You have a family history of thyroid problems.
- You have been diagnosed with chronic fatigue syndrome or pituitary or endocrine disorders.
- You are a woman at or near menopause, or you are pregnant, or you just had a baby.