- A movie starring Ashton Kutcher where current events are altered by changes in the past...
- The propensity of a system to be sensitive to initial conditions, and for the system becoming unpredictable over time, this idea gave rise to the notion of a butterfly flapping its wings in one area of the world causing a tornado in another remote area of the world...
- The changes in metabolism and physical appearance caused by a small, butterfly-shaped gland in one's throat. For the readers here, the third definition is what concerns us most and is the topic of this series of articles.
The thyroid is the butterfly shaped gland that impacts metabolism in adults. It responds to and is regulated by feedback loops and plays a vital role in maintaining body temperature and homeostasis.
Of significant concern to the weight trainer and bodybuilder, the thyroid gland regulates the amount of bodyfat you carry by manipulating how rapidly fuels are used for basic bodily maintenance and functions.
There are a lot of issues involved with the thyroid gland for the bodybuilder and I hope to cover some of them in this two-part article. I'll discuss the basics here in Part I and things you can do in Part II
The thyroid lies in front of your windpipe (trachea), just below your voice box (larynx). The thyroid is part of the endocrine system and produces, stores and releases hormones that affects your metabolism.
The thyroid gland uses iodine from the foods you eat to make these hormones. Additionally, the thyroid plays an important role in lipid regulation and has been shown to affect cholesterol levels.
There Are Some Significant Thyroid Health Issues To Consider1:
- Thyroid issues tend to be familial (i.e.; they run in the family).
- Thyroid issues tend to increase as you age.
- Thyroid issues affect women more than men.
- Thyroid issues and risks increase significantly for smokers.
- Thyroid issues are occurring in greater numbers in America now than in the past.
One of the more common issues involved with the thyroid gland is goiters. A goiter is a significant enlargement of the thyroid gland. Most all of us have seen pictures of people with goiters when we were in school.
With modern diet and medicine, goiters are not as common as they were in the past. However, thyroid disease afflicts more than 27 million Americans and is more prevalent than diabetes or heart disease.
A feedback loop controls the level of circulating thyroid hormone. The feedback loop involves three glands - the thyroid, pituitary and hypothalamus - working in harmony.
Problems with any of these three glands can lead to reduced performance and less than optimal health. Testing and diagnosis can pinpoint where the problem lies and an appropriate course of action for recovery.
The feedback loop for thyroid hormone maintenance is not too complex. The thyroid secretes thyroid hormone when signaled from the pituitary gland. The signal is actually Thyroid Stimulating Hormone (TSH) and increasing levels of TSH tells the thyroid gland to release more hormone.
TSH secretion is in turn controlled through release of Thyrotropin Releasing Hormone (TRH), which is produced and released by the hypothalamus. TRH release is based on circulating thyroid hormone levels in the blood stream, sensed by the hypothalamus.
As with most all hormones, levels of one hormone can affect levels of another hormone. TRH, for example, has a key role in thyroid hormone level and has also been linked to growth hormone, adrenaline and insulin secretion.
Low thyroid hormone levels have also been linked to elevated cholesterol levels. Thus, it is important to maintain hormone levels in proper balance to not only optimize growth, but also maintain health.
Thyroid Hormones (T2/T3/T4)
The major metabolites of thyroid hormone discussed are T4 (thyroxine), T3 (triiodothyronine) and T2 (diiodothyronines). The designation is rather straightforward, the T represents Thyroid Hormone and the number represents the number of Iodine molecules attached to the hormone.
There are other metabolites, such as monoiodothyronine (T1), but its impact is believed to be minor. The thyroid produces and releases T4 and T3 hormones.
The thyroid releases significantly more T4 hormone than T3 hormone. Inactive thyroid hormone is T4, while the active hormone is T3. T2 is also an active hormone, but it is rather different than T3.
T2 appears to be the active hormone in only the liver and brown adipose tissue (BAT), i.e., fat cells. Most of the literature will classify T2 as inactive because of this limited activity.
Both T4 and T2 are converted to T3 through separate mechanisms and different locations. The most common conversion is mediated by the enzyme deiodinase, which converts T4 into T3, by removal of an iodine atom. The table provides a summary of this information in this section.
|Primary Producer||Thyroid Thyroid||Intercellular||Intercellular|
|Activity||Inactive||Active||Active (Liver & BAT)|
Hypothyroid And Hyperthyroid
Hypothyroid and hyperthyroid are the two terms that are often discussed with thyroid health. Both signify poor thyroid health on the opposite sides of normal. To simplify the terms:
- Hypothyroid is the condition with a lack of thyroid hormone.
- Hyperthyroid is the condition when thyroid hormone is in excess.
Hypothyroidism is a condition that occurs when T4 levels drop and the body begins a metabolic slow down. Hypothyroidism was first diagnosed in the late nineteenth century when physicians observed swelling of the hands, face, feet, and tissues around the eyes after surgically removing the thyroid gland from patients. The syndrome was called myxedema and corresponds with the absence of thyroid hormones.
The term myxedema is still used today and is often associated with a severe lack of thyroid hormone that often leads to coma. Other common terms used in discussing hypothyroidism are autoimmune disease and Hashimoto's thyroiditis. Both of these ailments result in a less than fully functioning thyroid gland.
Hypothyroidism is usually progressive and irreversible, but today's treatment schedules are very successful and allow for full, normal living. Combined with the symptoms listed below in the table, a rising TSH level is a good indicator of a hypothyroid condition.
There are some unique risk factors associated with hypothyroidism. There are indications that individuals with ovarian failure, sleep apnea, premature gray hair and left-handedness are more likely to suffer from hypothyroidism.
Subclinical hypothyroidism is a more recent term used to identify increasing TSH levels and declining T4 levels.
Blood tests for T4 levels can still be normal and early symptoms of hypothyroidism may be exhibited.
Research is finding that subclinical hypothyroidism is very common (affecting about 10 million Americans). Fortunately, subclinical hypothyroidism does not often progress to the full-blown disorder in most people. However, some evidence suggests that even modest abnormal thyroid hormone levels may do some damage.
Hypothyroidism Signs & Symptoms
|Early Symptoms||Late Symptoms|
|Fatigue||Dry flaky skin|
|Cold intolerance||Thickening of the skin|
|Constipation||Puffy face, hands and feet|
|Weight gain (unintentional)||Decreased taste and smell|
|Depression||Thinning of eyebrows|
|Joint or muscle pain||Hoarseness||Thin, brittle fingernails and hair||Abnormal menstrual periods|
Hyperthyroidism, also known as thyrotoxicosis, is a clinical condition caused by excess quantities of thyroid hormone in the body. The condition may be caused by over production by the thyroid gland or the pituitary gland releasing excessive TSH.
The excess of hormones can cause heat intolerance, increased energy, difficulty sleeping, diarrhea and anxiety and other symptoms as listed in the table.
Graves' disease is the most common condition associated with hyperthyroidism. Graves' disease is a basic defect in the immune system that causes production of antibodies that stimulate and attack the thyroid gland. This attack on the thyroid causes growth of the gland and overproduction of thyroid hormone
Factitious hyperthyroidism is another hyperthyroid condition. It is associated with ingestion of excessive amounts of thyroid hormone. Thyroid hormone preparations have been available for over a century and taking excess prescription or glandular mixtures can also cause hyperthyroid conditions.
This is a condition that bodybuilders can fall into when taking thyroid hormones.
Hyperthyroidism Signs Symptoms
|Protruding eyes||Sleeping difficulty|
|Increased appetite||Clammy skin|
|Nervousness||Skin blushing or flushing|
|Heat intolerance||Nausea and vomiting|
|Increased sweating||Lack of menstruation|
|Fatigue||Itching - overall||Frequent bowel movements||Heartbeat sensations||Menstrual irregularities||Hand tremor||Goiter (visibly enlarged thyroid) may be present||Diarrhea||High Blood Pressure||Hair loss|
Abnormal thyroid hormone levels can cause a person to have sub-optimal metabolism, with protein synthesis and bodyfat use among the essential functions exhibiting degraded performance. The symptoms of abnormal thyroid function can indicate a problem, but only a blood test will confirm malfunction.
Because I work in the nuclear industry, my company provides an annual blood test with a thyroid panel. Radioactive iodine is a common fission product produced by nuclear power and it can damage the thyroid if ingested. For the protection of the workforce, we get tested annually for thyroid function.
A thyroid hormone panel, as part of a blood test, provides diagnostic information on the function of the gland.
Thyroid Hormone Blood Tests Often Include The Following Assessments (1)
Free Thyroxine Index (FTI or FT4)
Free thyroxine (T4) can be measured directly (FT4) or calculated (FTI). The FTI is a measure of the amount of T4 in relation to the amount of thyroxine-binding globulin present.
The FTI is calculated from the T4 and T3 uptake, or T3U, values. The FTI value can indicate when an abnormal level of thyroxin-binding globulin in the blood causes an abnormal level of T4. Typical levels range from 0.7-1.9 ng/dl
T3 has a greater effect on metabolism than T4, even though T3 is normally present in significantly lower amounts than T4. The total amount of T3 in the blood or the amount of free T3 (FT3) can be measured.
Normally, less than 1% of the T3 is free. Typical levels range from 40-220 ng/dl or 0.6-3.4 nmol/L.
Triiodothyronine Uptake (T3U)
The T3U test is an indirect measurement of the amount of the protein (thyroxine-binding globulin) that can bind to T3 and T4. The results of this test are useful only when evaluated along with other thyroid function tests.
Total Thyroxine (T4)
Most of the T4 in blood is attached to a protein (called thyroxine-binding globulin). Less than 1% of the T4 is unattached. A total T4 blood test measures both bound and free thyroxine.
Free thyroxine affects tissue function in the body, but bound thyroxine does not. And because most T4 is bound, this test is a far better indicator of the thyroid status. Typical levels range from 4.6-12 ug/dl or 51-154 nmol/L.
Thyroid Stimulating Hormone (TSH)
The TSH value provides an indication of how well the feedback mechanism and thyroid are functioning. Normal values are from 0.4 to 4.0 mIU/L for those with no symptoms of an under- or over-active thyroid.
Values below 0.4 are considered hyperthyroid, values 4.0 and slightly higher are considered sub clinical hypothyroid and values generally above 10 indicate full hypothyroid conditions.
When getting any tests performed, you should have some background knowledge to better understand the results. Most doctors are very good, but they are not infallible. Why do you think second opinions are often recommended?
You should have the basic knowledge to interpret test results. With the knowledge you can then challenge your medical professional for the most accurate assessment, and together, formulate a plan to optimize your health and bodybuilding and athletic progress.
Part 1 | Part 2
- American Association of Clinical Endocrinologist - Thyroid Awareness 2005
- Thyroid Hormone Tests, Web MD