Thyroid Panel

In order to fully diagnose thyroid disorders, the following labs are required. Note that many conventional medical practitioners use TSH as a screening tool, and run no further tests if TSH appears to be within normal limits. Dr. Weyrich prefers to run additional tests in any case where the symptom presentation suggests hypothyroidism, particularly if the axillary basal body temperature is below 97.8 degrees F or other symptoms of hypothyroidism present.

Practitioners differ on whether a person being treated for a thyroid condition should take their thyroid medication the morning before the test. Dr. Weyrich generally is interested in the hormone status as corrected by the supplemental thyroid hormone, and has his patients continue with their thyroid medication according to their regular schedule. Dr. Starr prefers to have his patients defer their morning dose until after the blood draw [Starr2005, pg 168].

Your doctor or lab may have different instructions that supersede the above.

Test Name	Name of Lab	Lab Code	Estimated Cost	Processing Time	Comments
TSH + total-T4 + total-T3 + reverse-T3		$201		Dr. Weyrich's standard workup
	Any Lab Test Now		$225
Sonora Quest		$449

Test Name	Name of Lab	Lab Code	Estimated Cost	Processing Time	Comments
TSH	Sonora Quest	8055	$57		Always run
	LabCorp	4259
total-T4	Sonora Quest	8045	$36		Always run
	LabCorp	1149
total-T3	Sonora Quest	8093	$122		Run if hypothyroid signs
	LabCorp	2188
reverse-T3	Sonora Quest	8127	$235		Run if hypothyroid signs
	LabCorp	2212
free-T4	Sonora Quest	9731			Run if hypothyroid signs
free-T3	Sonora Quest	15739 (tracer dialysis)			Run if hypothyroid signs
		9346 (non-dialysis)
Thyroglobulin Antibodies	Sonora Quest	9150			Run if Hashimoto's Thyroiditis is suspected. 70% sensitivity [Pagana2011, pg 103].
Microsomal Thyroid Peroxidase Antibodies	Sonora Quest	9145			Run if Hashimoto's Thyroiditis is suspected. 95% sensitivity [Pagana2011, pg 103].

Costs cited are subject to change and may be reduced by insurance or cash discounts and increased by sample collection fees.

Thyroid hormones regulate the energy metabolism of the body, acting much as a governor on a car or a thermostat. When the body is too hot or energy reserves are low, thyroid hormone is reduced. Conversely, when the body is too cold and energy reserves are high, thyroid hormone is increased.

Three main endocrine glands are involved in regulating thyroid hormone in the body: The hypothalamus and pituitary gland (in the brain) and the thyroid gland (in the throat). For a more in-depth treatment of thyroid hormone labs, see Dickson B. Dunlap: Thyroid Function Tests

The main hormones involved in the thyroid system are:

• TRH (Thyroid Releasing Hormone) - produced by the hypothalamus.
• TSH (Thyroid Stimulating Hormone) - produced by the pituitary gland.
• T4 (Thyroxine, tetraiodothyronine) - produced by the thyroid gland. Increases oxygen availability in all tissues [Friedman2005, pg 93].
• T3 (triiodothyronine) - made from T4, primarily in the liver and kidneys. Most active thyroid hormone; increases oxygen availability in all tissues and interacts with the mitochondria to increase energy production and thus regulate metabolic rate [Friedman2005, pg 93]; [Starr2005].

The three endocrine glands work together in a system of negative feedback, constantly monitoring and adjusting the status of the body:

• Low free-T4 levels in the blood prompts the hypothalamus to produce TRH.
• TRH prompts the anterior pituitary gland to produce TSH.
• TSH prompts the thyroid gland to release T4, which is produced by the thyroid gland.
• T4 is converted to T3 in the liver and kidneys.
• T3 is then disseminated in the blood throughout the body.
• If T4 or T3 levels rise too high, a negative feedback loop to the hypothalamus reduces TRH production to maintain homeostasis.

One author suggests that the peripheral cells have some signaling mechanism back to the hypothalamus to indicate a need for more circulating thyroid hormone, but does not make clear the nature of this signaling mechanism [Starr2005, pg 67]. Most authors consider free-T3 or free-T4 in the blood to be the primary signaling mechanism back to the hypothalamus.

TSH (Thyroid Stimulating Hormone)

When TSH is within the normal range, conventional medicine considers that the upper control centers in the brain hypothalamus and pituitary) have established homeostasis.

However, researchers have found that the symptom picture does not always correlate with TSH levels [Zulewski1997  🕮 ].

Practitioners of functional medicine note that in cases of peripheral resistance to T4, normal levels of TSH and T4 may be insufficient to eliminate the signs and symptoms of hypothyroidism. In this case, supplementation with desiccated thyroid or custom-formulated T4/T3 blend may be necessary to attain remission of symptoms, even though TSH may be driven to subnormal levels (less than 0.01) that most allopathic doctors consider indicative of hyperthyroidism [Starr2005, pg 63]

Total-T4

Total-T3

T3 is the most biologically active thyroid hormone. Low levels of total-T3 when compared with total-T4 indicate poor conversion of T4 into T3 by the peripheral tissues.

Reverse-T3

This is an inactive isomer of T3 that may be elevated when T3 is low. Elevated reverse-T3 may indicate a selenium deficiency or caloric restriction.

Free-T4

This is the fraction of total-T4 that is not bound to blood proteins and hence represents the amount of T4 actually available to the tissues. Free-T4 should be within the upper limit of normal [Starr2005, pg 168]. There are several different methods for measuring free-T4; The non-dialysis immunoassay) method is most commonly used. However, according to Mayo Clinic "abnormal types or quantities of binding proteins found in some patients and most often related to other illnesses or drug treatments, may interfere in the accurate measurement of free-T4 by analog immunoassays. These problems can be overcome by measuring free-T4 by equilibrium dialysis, free from interfering proteins." See also Sonora Quest

Free-T3

This is the fraction of total-T3 that is not bound to blood proteins and hence represents the amount of T3 actually available to the tissues. Free-T3 may be elevated if thyroid medications are taken in the morning before the blood draw, otherwise should be within the upper limit of normal [Starr2005, pg 168].

24 hour Urine T3

Another approach that has been discussed in the literature is an assay of T3 in 24-hour sample of urine. While this test is reported to accurately correlate with symptoms of hypothyroidism, the test is not widely used (yet) [Starr2005, pg 71]; [Hertoghe2001].