How it works

Find Center

About us

HOME

Over 1800
Service Centers

THYROID  PROFILE

Includes Temp Log - T3 uptake -T4 -T7 FTI

Temp Log

The symptoms of a low body temperature are classic for low thyroid function and they often get better with thyroid medicine. Body temperatures are normally lower in the morning, higher in the afternoon, and lower again in the evening. So if the temperatures are low during the day when they're supposed to be at their highest, that's better evidence that there's a problem. Temperature patterns are also important and illuminating. How patients feel can be affected not only by how high or low their temperatures are but also on how steady their temps are. One temperature reading a day is not enough to see how widely the temperature is fluctuating, but more than three a day can be too time consuming.
 

T3 uptake

This test measures the amount of triiodothyronine, or T3, in the blood. T3 is one of two major hormones produced by the thyroid gland (the other hormone is called thyroxine, or T4). The thyroid gland is a small butterfly-shaped organ that lies flat across your windpipe. The hormones it produces control the rate at which the body uses energy. Their production is regulated by a feedback system. When blood levels of thyroid hormones decline, the hypothalamus (an organ in the brain) releases thyrotropin releasing hormone, which stimulates the pituitary (a tiny organ below the brain and behind the sinus cavities) to produce and release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland to produce and/or release more thyroid hormones. Most of the thyroid hormone produced is T4. This hormone is relatively inactive, but it is converted into the much more active T3 in the liver and other tissues.

If the thyroid gland produces excessive amounts of T4 and T3, then the patient may have symptoms associated with hyperthyroidism, such as nervousness, tremors of the hands, weight loss, insomnia, and puffiness around dry, irritated eyes. In some cases, the patient’s eyes cannot move normally and they may appear to be staring. In other cases, the patient’s eyes may appear to bulge.

If the thyroid gland produces insufficient amounts of thyroid hormones, then the patient may have symptoms associated with hypothyroidism and a slowed metabolism, such as weight gain, dry skin, fatigue, and constipation. Blood levels of hormones may be increased or decreased because of insufficient or excessive production by the thyroid gland, due to thyroid dysfunction, or due to insufficient or excessive TSH production related to pituitary dysfunction.
 

Fatigue

About 99.7% of the T3 found in the blood is attached to a protein (primarily thyroxine-binding globulin ( TBG) but also several other proteins) and the rest is free (unattached). Separate blood tests can be performed to measure either the total (both bound and unattached) or free (unattached) T3 hormone in the blood.
When TBG is increased, T3 uptake is decreased, and vice versa. T3 Uptake does not measure the level of T3 or T4 in serum.

Increased T3 uptake (decreased TBG) is seen in chronic liver disease, protein-losing states, and with use of the following drugs: androgens, barbiturates, bishydroxycourmarin, chlorpropamide, corticosteroids, danazol, d-thyroxine, penicillin, phenylbutazone, valproic acid, and androgens. It is also seen in hyperthyroidism.

Decreased T3 uptake (increased TBG) may occur due to the effects of exogenous estrogens (including oral contraceptives), pregnancy, acute hepatitis, and in genetically-determined elevations of TBG. Drugs producing increased TBG include clofibrate, lithium, methimazole, phenothiazines, and propylthiouracil. Decreased T3 uptake may occur in hypothyroidism
 

T4

T4 is one of two major hormones produced by the thyroid gland (the other is called triiodothyronine, or T3). The thyroid is a small, butterfly-shaped gland located just below the Adam's apple. This gland plays a vital role in controlling the rate at which your body uses energy.

The body has a feedback system that turns thyroid hormone production on and off. When the level of T4 in the bloodstream decreases, the hypothalamus (an organ in the brain) releases thyrotropin releasing hormone, which stimulates the pituitary gland (an organ below the hypothalamus) to release thyroid-stimulating hormone (TSH), which in turn stimulates the thyroid gland to make and/or release more T4. As blood concentrations of T4 increase, the amount of TSH released decreases.

T4 makes up nearly all of what we call thyroid hormone, while T3 makes up less than 10%. Inside the thyroid gland, T4 is produced, bound to a protein called thyroglobulin, and stored. When the body requires thyroid hormone, the thyroid gland produces some T4 or T3 and/or releases stored T4 into circulation. In the blood, T4 is present in a free (not bound) and protein-bound form (primarily bound to thyroxine-binding globulin). The concentration of free T4 is only about 0.1% of that of total T4, but the free T4 is the portion of thyroxine that is active. T4 only becomes an active thyroid hormone when it is converted into T3 in the liver or other tissues.

If the thyroid gland does not produce sufficient T4 (due to thyroid dysfunction or to insufficient TSH), then the affected patient experiences symptoms of hypothyroidism such as weight gain, dry skin, cold intolerance, irregular menstruation, and fatigue. If the thyroid gland produces too much T4, the rate of the patient’s body functions will increase and cause symptoms associated with hyperthyroidism such as increased heart rate, anxiety, weight loss, difficulty sleeping, tremors in the hands, and puffiness around dry, irritated eyes.

The most common causes of thyroid dysfunction are autoimmune-related Graves' disease causes hyperthyroidism and Hashimoto's thyroiditis causes hypothyroidism. Both hyper- and hypothyroidism can also be caused by thyroiditis (thyroid inflammation), thyroid cancer, and excessive or deficient production of TSH. The effect of these conditions on thyroid hormone production can be detected and monitored by measuring the total T4 (includes bound and free portion) or the free T4 (only unbound).
This is a measurement of the total thyroxine in the serum, including both the physiologically active (free) form, and the inactive form bound to thyroxine-binding globulin (TBG). It is increased in hyperthyroidism and in euthyroid states characterized by increased TBG (See "T3 uptake," above, and "FTI," below). Occasionally, hyperthyroidism will not be manifested by elevation of T4 (free or total), but only by elevation of T3 (triiodothyronine). Therefore, if thyrotoxicosis is clinically suspect, and T4 and FTI are normal, the test "T3-RIA" is recommended (this is not the same test as "T3 uptake," which has nothing to do with the amount of T3 in the patient's serum).  
T4 is decreased in hypothyroidism and in euthyroid states characterized by decreased TBG. A separate test for "T4" is available, but it is not usually necessary for the diagnosis of functional thyroid disorders.

T7 (FTI)

This is a convenient parameter with mathematically accounts for the reciprocal effects of T4 and T3 uptake to give a single figure which correlates with free T4. Therefore, increased FTI is seen in hyperthyroidism, and decreased FTI is seen in hypothyroidism. Early cases of hyperthyroidism may be expressed only by decreased thyroid stimulation hormone (TSH) with normal FTI.

go back

This test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland, a tiny organ located below the brain and behind the sinus cavities. It is part of the body’s feedback system to maintain stable amounts of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) in the blood. Thyroid hormones help control the rate at which the body uses energy. When concentrations decrease in the blood, the hypothalamus (an organ in the brain) releases thyrotropin releasing hormone (TRH). This stimulates the release of TSH by the pituitary gland, and then TSH in turn stimulates the production and release of T4 and T3 by the thyroid gland, a small butterfly-shaped gland that lies flat against the windpipe. When all three organs are functioning normally, thyroid production turns on and off to maintain blood thyroid hormone levels.

If there is pituitary dysfunction, then increased or decreased amounts of TSH may result. If TSH concentrations are increased, the thyroid will make and release inappropriate amounts of T4 and T3 and the patient may experience symptoms associated with hyperthyroidism (overactive thyroid), such as rapid heart rate, weight loss, nervousness, hand tremors, irritated eyes, and difficulty sleeping. If there is decreased production of thyroid hormones (hypothyroidism), then the patient may experience symptoms such as weight gain, dry skin, constipation, cold intolerance, and fatigue. In addition to pituitary dysfunction, hyper- or hypothyroidism can occur if there is a problem with the hypothalamus (insufficient or excessive TRH). They may also occur with a variety of thyroid diseases that affect thyroid hormone production regardless of the amount of TSH present in the blood

Early cases of hypothyroidism may be expressed only by increased TSH with normal T7 FTI. Currently, the method of choice for screening for both hyper- and hypothyroidism is the serum TSH. Modern methodologies ("ultra sensitive TSH") allow accurate determination of the very low concentrations of TSH at the physiological cutoff between the normal and hyperthyroid states
 TSH has been recognized as an exquisitely sensitive indicator of thyroid status. TSH assays (second or third generation) have therefore been widely adopted as the front-line thyroid function test. In ambulatory patients with intact hypothalamic and pituitary function, a normal TSH result excludes hypo or hyperthyroidism; whereas elevated and suppressed TSH results are diagnostic of hypo and hyperthyroidism, respectively.

go back

Reverse T3

go back