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Sub Clinical Hypothyroidism: Fatigue, Depression or Weight Gain


Many people suffer from the symptoms associated with hypothyroidism. Some actually have this condition in a form that a doctor is likely to identify; some have unrelated conditions that can look like hypothyroidism but the majority have a condition referred to as subclinical hypothyroidism. This refers to a situation where the lab numbers are not out of range but they reflect a level of dysfunction significant enough to cause symptoms. Unfortunately, most health practitioners will not identify a thyroid problem unless the numbers are outside of the reference range.

Symptoms of Hypothyroidism
  • Fatigue
  • Weakness
  • Weight gain or increased difficulty losing weight
  • Coarse, dry hair
  • Dry, rough pale skin
  • Hair loss
  • Cold intolerance (can't tolerate the cold like those around you)
  • Muscle cramps and frequent muscle aches
  • Constipation
  • Depression
  • Irritability
  • Memory loss
  • Abnormal menstrual cycles
  • Decreased libido


It is very important to be an educated patient and to know what lab values may suggest that your thyroid function is not optimal even if your current doctor is not recognizing it. I have seen many people who have been told that their thyroid numbers were fine despite having symptoms of low energy, weight gain, hair loss and depression. Invariable they were recommended to start anti-depressant medication. Upon further investigation and more detailed thyroid studies it was clear that their symptoms were more related to low thyroid function rather than from a true case of depression.

Understanding the lab tests:
Standard lab tests for thyroid function include TSH, T4 and T3 uptake. Although these can be valuable, there are more specific tests that better reflect how thyroid function is affecting your health and metabolism. The best thyroid test combination for most people is a TSH, Free T4 and Free T3.

TSH:
The TSH is a measure of how much your body desires thyroid hormone. When the TSH is too low the body is telling us that it wants the thyroid to back off of hormone production. This most often occurs when people have overactive thyroids (hyperthyroidism). If the TSH is elevated, we know that the body is asking the thyroid to do more work and produce more hormones. The TSH will be elevated in hypo-thyroidism because a sluggish thyroid will have trouble keeping up with adequate hormone levels. The technical reference range for TSH on lab work is from 0.5-5.5. Usually as long at it falls in that range doctors will give you the stamp of approval. However, there is a range I refer to as the "optimal range" which is a reflection of where the TSH should be if your thyroid gland is working in a manner that produces optimal metabolism and physiologic function. This optimal range is very narrow and exists between about 1.2 and 2.2 for TSH. This information is based on rigorous clinical trials. In publishing new clinical guidelines in 2002, the American Association of Clinical Endocrinologists fairly dramatically formalized a reversal of its previous doctrine, establishing a narrower "normal" TSH margin of 0.3–3.0. If your TSH is above 2.2, and certainly if it is above 3 you very likely have subclinical hypothyroidism.

Free T4:
T4 is the main thyroid hormone, consisting of 99% of circulating hormone. The word "free" indicates that it is being measured in it’s free state vs. it bound state. All hormones in the body must travel around bound to protein carriers. In the bound state they are inactive. It is only once the hormone has been released from its carrier that it has the capability to influence cellular activity. By measuring free hormone levels we get an accurate representation of the amount of thyroid hormone actually available to benefit our cells. Estrogen and testosterone imbalances, stress, nutritional deficiencies and genetics can all determine how much hormone is free and how much is bound. Like TSH, Free T4 also has narrow optimal range. Most practitioners skilled in working with subclinical hypothyroidism like to see Free T4 levels between 1.2 and 1.3.

Free T3:
T4 is technically classified as a pre-hormone and must be converted into its activated counter-part in order to turn on cellular metabolism. The activated counter part is T3 which represents only about 1% of circulating thyroid hormone. Don’t be fooled by its low circulating percentage, T3 is 99% more biologically active than T4 when it comes to actually stimulating metabolism. Again, we are measuring the “free” hormone as this is the only one we are interested in when assessing actual hormonal influences on our cells. Optimal range for free T3 is 3.3 or depending on the measuring unit 330.

One of the most important factors in subclinical hypothyroidism is the ability of an individual to effectively convert T4->T3. If this process is hindered significantly it will result in presentation of hypo-thyroid symptoms as there is a reduction in the amount of active hormone being produced. The most common reason for poor T4->T3 conversion is a simple nutritional deficiency and can easily be corrected. Selenium, zinc and B6 are the most common nutrients associated with improving conversion capability.

This is the hardest form on subclinical hypothyroidism to pick up because the TSH and the T4 often look totally normal. Due to the fact that most practitioners only measure TSH and T4 the thyroid picture will look totally normal. Free T3 levels are very rarely ordered on routine blood tests mainly because they are thought to be expensive. However, with recent advances of lab technology Free T3 levels are very affordable and easy to acquire. Many practitioners rely on the T3 uptake test to asses T3 levels not realizing that T3 uptake is a test designed to measure T4 levels. Ninety five percent of thyroid screens done in this country never measure T3 levels and thus never assess the levels of active thyroid hormone.

If you have symptoms of hypo-thyroidism it is important to make sure that all the appropriate lab tests are done and interrupted in the correct way. It is best to assume that your practitioner is not familiar with subclinical hypothyroidism so it will be your job to adequately educate them about what lab tests you would like and why.