Thyroid diseases may prevent you from getting pregnant.
Thyroid hormone profile
TSH, FT4, FT3 tests are performed in order to exclude thyroid diseases which prevent getting pregnant. Hormone levels are measured on the basis of blood sample examination.
TSH test
Thyroid-stimulating hormone (thyrotropin, TSH) is produced by the pituitary gland. The test of its concentration in blood allows to assess the functioning of the thyroid gland and detect its diseases (hypothyroidism and hyperthyroidism) even before the appearance of the first symptoms. It is best to collect a blood sample for testing in the morning, as TSH levels may vary during the day. You don't have to prepare for the test, but you should inform your physician about the drugs you are taking before it is performed, because in some cases it is necessary to stop taking them for a short time.
The correct thyrotropin concentration is between 0.4 and 5 mIU/L. Higher levels of thyrotrophic hormone suggest hypothyroidism and moreover they may be a symptom of pregnancy. Lower levels of TSH hormone indicate hyperthyroidism and may also be related to drugs (e.g. steroid drugs), Graves’ disease, excess iodine in the body or excessive doses of drugs containing thyroid hormones.
The result of the thyrotropin test is not sufficient to make a diagnosis - fT3 (free triiodothyronine) and fT4 (free thyroxine) are also usually measured.
fT3 test
Thyroid diseases may cause a decrease in fertility in women, so it is worthwhile to examine the level of thyroid hormones after fruitless efforts to conceive. One of them is fT3, i.e. free triiodothyronine. The examination of fT3 concentration in the blood allows to assess the functioning of the thyroid gland and detect its diseases - however, in order to make a diagnosis, it is necessary to establish values for other hormones from this group, namely TSH (thyrotropic hormone) and fT4 (free thyroxine).
A venous blood sample is needed, taken at any time. The patient needn't fast before the test. A high concentration of free triiodothyronine suggests excessive activity of the thyroid gland (the so-called hyperactivity), but may also indicate iodine deficiency in the body. A low fT3 result indicates hypothyroidism, and may be related to another infectious disease or surgery.
fT4 test
The proper functioning of the whole body- including the reproductive system - depends largely on the proper functioning of the thyroid gland and the amount of hormones it produces. One of them is the fT4 hormone (the so-called free thyroxine), which regulates the course of metabolic processes. The examination of fT4 levels in blood is used to assess the functioning of the thyroid gland and to monitor the effectiveness of treatment in diagnosed disease within this organ.
You can take a blood sample for testing at any time of the day, without having to be fasting. Elevated levels of free thyroxine may indicate hyperthyroidism or the excess of thyroid hormones in the body resulting from the use of hormonal drugs. Low fT4 values as a result of the test indicate hypothyroidism or severe iodine deficiency.