Thyroid is a hot topic and at times controversial, mainly around thyroid management. The thyroid is a butterfly-like shaped gland consisting of two lobes joined by a narrow strip, called the isthmus. It is composed of small sacs called follicles that absorb iodine from the blood for the production of thyroid hormones. In this blog, we’re going to identify the main thyroid hormones, the symptoms one might experience from hypothyroidism, the types of testing available, and what type of treatment is available.
Thyroid Hormones
There are two main thyroid hormones. One is triiodothryonine, or T3, because it has 3 iodine atoms. And the other is thyroxine, or T4, because it has 4 iodine atoms. When the pituitary senses low blood levels of thyroid hormones, it sends a message to the hypothalamus. The hypothalamus then releases thyrotropin-releasing hormone (TRH), which then travels to the pituitary. The pituitary signals production of thyroid-stimulating hormone (TSH). TSH travels to the thyroid resulting in the production of T3 and T4. When the blood levels are high, there is a negative feedback, stopping the production of TRH and TSH. Think of this process as a furnace. You turn up the heat, increasing thyroid production and metabolism. When the temperature is reached, the thermostat (the pituitary) turns off.
Thyroid cells are the only cells in the body that can absorb iodine. Thyroid cells produce about 80% T4 and 20% T3. Iodine is key to production and most of the T4 is converted into T3 by removal of an iodine atom. T3 is the more active form of the hormone.
Signs of Hypothyroidism
Before I get into the proper testing of thyroid hormones, here is a list of signs/symptoms. Many of these symptoms can be confused with other problems and are also very similar to low progesterone levels as well.
- Tingling in the fingers
- Constipation
- Memory/Cognitive impairment
- Weight gain
- Cold intolerance
- Coarseness or loss of hair
- Depression
- Infertility or miscarriages
- Decreased libido
- Muscle stiffness, cramps, pain
- Drooping eyelids
- Loss of outer 1/3 of eyebrows
- Hoarseness
- Decreased concentration
- Dry skin
- Goiter
- Irregular or heavy menstruation
- Slowed heart rate
- Delayed tendon relaxation
- Fatigue
- Puffiness in face
Testing Thyroid Hormones
If you or your healthcare provider suspect a thyroid hormone imbalance, there are convenient tests that can be done at home.
TSH
Measuring thyroid-stimulating hormone is the most common thyroid test. A high TSH indicates failure of the thyroid to produce enough hormone (primary hypothyroidism). A low TSH indicates overactive thyroid (hyperthyroidism). Occasionally, a low TSH is actually secondary hypothyroidism- which is a result of the pituitary gland not making enough TSH to stimulate the thyroid. This is a good reason to test other thyroid hormones.
One of the more controversial issues with testing TSH is the “normal” ranges. Most agree on the lower limit of 0.3 or 0.4mIU/L, the lower limit can vary widely. The American Association of Clinical Endocrinologists suggests a range of 0.3-3 mIU/L, whereas the Mayo Clinic uses a range of 0.3 to 5 mIU/L. This lower limit of 0.3-3 mIU/L, would result in a four-fold increase in the number of patients diagnosed with hypothyroidism.
It has been suggested that until the upper limit ranges have been determined, practitioners should settle on 0.4-4 mIU/L. It is also said that patients whose test results are 2.5 or above should be closely monitored and that thyroid supplementation should be prescribed for those showing clinical symptoms. Also note that TSH levels are higher early morning than in the afternoon.
Free T4
Free T4 (FT4) represents the level of hormone that the body has available to use and is not bound to protein. The normal range for Free T4 is 0.7-1.9 mg/dl. Using a combination of TSH and Free T4 increases the accuracy of the diagnosis.
HIGH TSH; LOW FT4 = Primary hypothyroidism
LOW TSH; LOW FT4 = Secondary hypothyroidism
LOW TSH; HIGH FT4 = Hyperthyroidism
Free T3
Free T3 (FT3) also measures the unbound hormone. Free T3 is typically elevated in hyperthyroidism and lowered in hypothyroidism. A normal range is 230-619 pg/d.
There are other tests for goiters, Grave’s disease and thyroid cancers, but I will only touch on two more relevant to this blog topic.
Thyroid Peroxidase Antibodies- (TPO)
These antibodies work against thyroid peroxidase, an enzyme that plays a part in the T4 to T3 conversion. TPO antibodies are present in 95% of patients with Hashimoto’s disease. Hashimoto’s is the most common cause of hypothyroidism.
Reverse T3- (RT3)
Reverse T3 can be used to determine if the body is converting T4 into an inactive form of T3, instead of an active form. This usually occurs in cases of extreme stress and is called Wilson’s Syndrome. It is considered quite controversial and some practitioners doubt the existence of Wilson’s Syndrome.
Hormone Replacement
Once hypothyroidism has been diagnosed, a thyroid hormone is supplemented. The most common prescription is for a synthetic form called Levothyroxine (Synthroid, Levoxyl) these products contain only T4 hormone. Typically, in the body, most of the T4 hormone is converted into the active hormone T3. However, patients who are treated for hypothyroidism have been found to have impaired T4 to T3 conversion. Consider using a more natural thyroid made from desiccated thyroid glands of pigs. They contain both T4 and T3 hormones (Armour, Nature-Throid, and Westhroid or customized compounded thyroid).
If you read the beginning paragraphs, you will remember that iodine plays a very important role in thyroid function. With people using less iodized salt and more sea salt, many people are deficient. Goiters are occurring more frequently than in the recent past. Please consider using an iodine supplement to support your thyroid.
It’s important to remember that a variety of issues can cause symptoms similar to hypothyroidism. With proper testing and guidance from your healthcare provider, an individualized treatment plan can help you live a healthy, normal life.