Are the common thyroid tests enough to diagnose hypothyroidism?
TSH (thyroid-stimulating hormone) test is the most important and sensitive test for hypothyroidism. It measures how much of the thyroid hormone thyroxine (T4) the thyroid gland is being asked to make. An abnormally high TSH means hypothyroidism: the thyroid gland is being asked to make more T4 because there isn’t enough T4 in the blood.
T4 tests: Most of the T4 in the blood is attached to a protein called thyroxine-binding globulin. The “bound” T4 can’t get into body cells. Only about 1%–2% of T4 in the blood is unattached (“free”) and can get into cells. The free T4 and the free T4 index are both simple blood tests that measure how much unattached T4 is in the blood and available to get into cells.
T3 tests: These check for levels of the hormone triiodothyronine. It's usually ordered if T4 tests and TSH tests suggest hyperthyroidism. It is not necessary to diagnose hypothyroidism. In a very rare form of hypothyroidism due to pituitary dysfunction, it may be necessary to order T3 tests.
Once someone is on established thyroid hormone treatment for hypothyroidism, TSH is adequate to monitor response to treatment.
How often do I need to get my thyroid levels checked?
When your caregiver first starts you on thyroid medication and whenever a change is made, they are likely to ask you to get your TSH checked 6-8 weeks later. Once you are on a stable dose of thyroid medication, most people only require labs once in 6 months or once a year.
If you become pregnant, you must contact your caregiver immediately and they will check your thyroid levels every 4 weeks for the first twenty weeks of your pregnancy and every 6 weeks after that and adjust your thyroid hormone dose if needed. Most women require more thyroid hormone in pregnancy.
How do I take thyroid hormone?
Because thyroid hormone stays in your system for a long time, it is best to take it just once a day. Take it first thing in the morning on an empty stomach, because some foods can affect the way your body absorbs thyroid hormone.
If you have trouble taking it on an empty stomach, just be sure to take it around the same time and the same way every day. If you miss a dose in the morning, take it as soon as you remember. If you do miss a day, it is is safe to take two pills the next day, one in the morning and one in the evening.
If you have a busy schedule in the morning, you may find it easier to take your thyroid medication at night before going to bed.
Most people on thyroid hormone need to take it for the rest of their lives. Do not stop taking your thyroid pills without talking with your caregiver.
How do we choose the right dose of thyroid hormone?
Your doctor will prescribe your dose based on your age, weight and other medical conditions. Most people require one or two dose adjustments to get them to their target, based on lab work done usually 6-8 weeks after starting the medication. A TSH (a blood test that measures this hormone) is usually all that is needed, unless you are on a thyroid hormone preparation that contains a combination of T4 and T3.
Is Brand name thyroid medication better than generic ?
There are several brand names and generic preparations of thyroid hormone available. Generic formulations are usually less costly. Although these all contain the same synthetic T4, there are different inactive ingredients in each of the brand names.
Recent studies have not shown any difference between brand name and generic thyroid medications in normalizing thyroid levels. In general, it is best for you to stay on the same formulation, whether generic or brand name. If a change in brand name is made, we encourage you to contact your caregiver so they can check your thyroid labs to make sure your levels are okay.
Is there a natural thyroid hormone replacement?
Yes—desiccated (dried and powdered) animal thyroid (Armour®), now mainly obtained from pigs, was the most common form of thyroid therapy before the individual active thyroid hormones were discovered.
Desiccated thyroid pills have chemicals (binders) in them to hold the pill together, so they are not completely “natural.”
Are natural thyroid hormones better than synthetic?
Desiccated animal thyroid is rarely prescribed today, and there is no evidence that desiccated thyroid has any advantage over synthetic T4.
Pills made from animal thyroid contain hormones and proteins that do not exist in the body outside of the thyroid gland. While desiccated thyroid contains both T4 and T3, the balance of T4 and T3 in animals is not the same as in humans – so the hormones in animal thyroid pills aren’t considered “natural” for the human body. The amounts of both T4 and T3 can vary in every batch of desiccated thyroid, making it harder to keep blood levels right.
Is a combination of T4 and T3 superior to T4 alone?
Some hormone preparations containing both T4 and T3 are available in the United States. Combination T4/T3 preparations contain much more T3 than is usually produced naturally within the body. Because of this, they can have the same side effects as T3 given by itself.
It is also given once a day, although T3 has a shorter half life and should ideally be taken twice a day. There has been interest in whether a combination of T4 and T3, with a lower amount of T3 given more than once a day, might result in better treatment of hypothyroidism, especially in those patients that do not feel completely normal on T4 alone. In these cases, Cytomel® (T3) is taken in addition to T4. A trial period of 3 – 6 months is reasonable to determine if combination T4 and T3 therapy will help.
Will thyroid hormone help me if I have hypothyroid symptoms but my thyroid blood work is normal?
Some people with normal thyroid blood tests have symptoms that are similar to symptoms of hypothyroidism. Several scientific studies have looked at whether T4 therapy would be of benefit to patients with symptoms that overlap with hypothyroid symptoms and normal thyroid function. In all cases, there was no difference between T4 and a placebo (sugar pill) in improving symptoms or well-being.
Can hyperthyroidism cause weight loss?
The Basal Metabolic Rate (BMR) in patients with hyperthyroidism is elevated, so many patients with an overactive thyroid have some weight loss.
Weight loss is related to the severity of the overactive thyroid. For example, if the thyroid is extremely overactive, your BMR increases which leads to increased calories needed to maintain the body weight. If the person does not increase the amount of calories eaten to match the excess calories burned, then there will be weight loss.
The factors that control our appetite, metabolism, and activity are very complex and thyroid hormone is only one factor in this complex system. On average, however, the more severe the hyperthyroidism, the greater the weight loss observed. Weight loss can also occur if the dose of thyroid hormone pills is too high for a patient. Since hyperthyroidism also increases appetite, some patients may not lose weight, and some may actually gain weight, depending on how much they increase their caloric intake.
Why do I gain weight after treating my hyperthyroidism?
Because hyperthyroidism is an abnormal state, we can predict that any weight loss caused by the abnormal state would go away when the abnormal state is reversed. This is indeed what we find. On average, any weight lost during the hyperthyroid state is regained when the hyperthyroidism is treated. Weight gain can even occur when there was little or no weight loss because patients may have gotten used to eating more calories because of the extra energy expenditure during hyperthyroidism.
Does Hypothyroidism cause weight gain?
Since the Basal Metabolic Rate(BMR) in patients with hypothyroidism is decreased, an underactive thyroid is generally associated with some weight gain. This decrease in BMR is very modest – weight gain in hypothyroidism is usually minimal. In general, people who have more severe hypothyroidism gain more weight. Massive weight gain is rarely associated with hypothyroidism.
Average weight gain with hypothyroidism is about 5-10 pounds, depending on the severity of the hypothyroidism. Finally, if weight gain is the only symptom of hypothyroidism that is present, it is less likely that the weight gain is solely due to the thyroid.
How much weigh can I expect to lose after treatment of my hypothyroidism?
Since much of the weight gain in hypothyroidism is excess salt and water, when the hypothyroidism is treated one can expect a small (usually less than 10% of body weight) weight loss.
Treatment of the abnormal state of hypothyroidism with thyroid hormone results in a return of body weight to what it was before the hypothyroidism developed. Since weight gain may have many causes and develops over a long period of time, it is fairly common to find that there is not a large amount of weight loss after successful treatment of hypothyroidism.
If all of the symptoms of hypothyroidism other than weight gain resolve with thyroid hormone treatment, it is unlikely that the weight gain was solely due to the thyroid. Once hypothyroidism has been treated and thyroid hormone levels are in the normal range, the ability to gain or lose weight is the same as in individuals who do not have thyroid problems.
What is Hashimoto’s thyroiditis?
Hashimoto’s thyroiditis (thyroiditis means "inflammation of the thyroid gland") is an autoimmune disorder involving chronic inflammation of the thyroid. Also known as chronic lymphocytic thyroiditis, it is the most common cause of hypothyroidism in the United States.
This condition tends to run in families. Over time, the ability of the thyroid gland to produce thyroid hormones often becomes impaired and leads to a gradual decline in function and eventually an underactive thyroid (Hypothyroidism). Hashimoto’s thyroiditis occurs most commonly in middle aged women, but can be seen at any age, and can also affect men and children.
What are the symptoms of Hashimoto’s thyroiditis?
There are no signs or symptoms that are unique to Hashimoto’s thyroiditis.
Because the condition usually progresses very slowly over many years, people with Hashimoto’s thyroiditis may not have any symptoms early on, even when the characteristic thyroid peroxidase (TPO) antibodies are detected in blood tests. TPO is an enzyme that plays a role in the production of thyroid hormones. If Hashimoto’s thyroiditis causes cell damage leading to low thyroid hormone levels, patients will eventually develop symptoms of hypothyroidism, but there is no evidence that the antibodies alone in the absence of hypothyroidism cause any symptoms.
Hypothyroid symptoms may include fatigue, weight gain, constipation, increased sensitivity to cold, dry skin, depression, muscle aches and reduced exercise tolerance, and irregular or heavy menses. In some cases, the inflammation causes the thyroid to become enlarged (goiter), which rarely may cause neck discomfort or difficulty swallowing.
How is Hashimoto’s thyroiditis diagnosed?
The diagnosis of Hashimoto’s thyroiditis may be made when patients present with symptoms of hypothyroidism, often accompanied by a goiter (an enlarged thyroid gland) on physical examination, and laboratory testing of hypothyroidism, which is an elevated thyroid stimulating hormone (TSH) with or without a low thyroid hormone (Free thyroxine [Free T4]) levels. TPO antibody, when measured, is usually elevated.
Occasionally, the disease may be diagnosed early, especially in people with a strong family history of thyroid disease. TPO antibody may be positive, but thyroid hormone levels may be normal or there may only be isolated mild elevation of serum TSH is seen. Symptoms of hypothyroidism may be absent.
How is Hashimoto’s thyroiditis treated?
Patients with elevated TPO antibodies but normal thyroid function tests (TSH and Free T4) do not require treatment.
Patients with only a slightly elevated TSH (mild hypothyroidism) may not require medication and should have repeat testing after 3-6 months.
For patients with overt hypothyroidism (elevated TSH and low thyroid hormone levels) treatment consists of thyroid hormone. Synthetic levothyroxine is an inexpensive pill that is very effective in restoring normal thyroid hormone levels, and results in an improvement of symptoms of hypothyroidism.
Most patients with Hashimoto’s thyroiditis will require lifelong treatment with levothyroxine. Finding the appropriate dose, particularly at the beginning, may require testing with TSH every 6-8 weeks after any dose adjustment, until the correct dose is determined. After that, monitoring of TSH once a year is generally sufficient.
When levothyroxine is taken in the appropriate dose, it has no side effects. However, when an insufficient dose is taken, serum TSH remains elevated and patients may have persistent symptoms of hypothyroidism .If the dose is excessive, serum TSH will become suppressed and patients may develop symptoms of hyperthyroidism or have other side effects
What is the relationship between thyroid and metabolism?
There is a complex relationship between thyroid disease, body weight and metabolism. Thyroid hormone regulates metabolism in both animals and humans. Metabolism is calculated by measuring the amount of oxygen used by the body over a specific amount of time.
If the measurement is made at rest, it is known as the basal metabolic rate (BMR). Measurement of the BMR was one of the earliest tests used to assess a patient’s thyroid status. Patients whose thyroid glands were not working were found to have low BMRs, and those with overactive thyroid glands had high BMRs.
Later studies linked these observations with measurements of thyroid hormone levels and showed that low thyroid hormone levels were associated with low BMRs and high thyroid hormone levels were associated with BMRs. Most physicians no longer use BMR due to the complexity in doing the test and because the BMR is subject to many influences other than the thyroid state.
What is relationship between BMR and weight?
Differences in BMRs are associated with changes in energy balance. Your energy balance is the difference between the number of calories you eat and the number of calories your body uses. A negative energy balance (more calories out than in) leads to weight loss. A positive energy balance (more in than out) leads to weight gain. Studies suggest that changes in thyroid hormone levels, which lead to changes in BMR, should also cause changes in energy balance and similar changes in body weight.
However, BMRs are not the whole story relating weight and thyroid – the relationship between metabolic rates, energy balance, and weight changes is very complex. There are many other hormones (besides thyroid hormone), proteins, and other chemicals that are very important for controlling energy expenditure, food intake, and body weight.
Because all of these substances interact with the parts of the brain and body that control energy expenditure and energy intake, we cannot predict the effect of changing only one of these factors (such as thyroid hormone) on body weight as a whole. For now, we can't say for sure if changing your thyroid state will change your body weight.
Does thyroid cancer affect TSH levels?
If you have surgery for thyroid cancer, you will need thyroid hormone to replace the function of the removed thyroid gland. Thyroid hormone will also keep any remaining thyroid cancer cells from growing.
What is thyroid hormone suppression therapy?
Thyroid hormone suppression therapy is an important part of thyroid cancer treatment for some patients. This therapy works to stop microscopic thyroid cancer cells, or leftover thyroid cancer, from growing.
For certain patients, the benefit of preventing cancer growth outweighs the risks, which include:
- A mild increase in the risk of fast, irregular heart rhythms
- Worsening chest pain
- Decreased bone density.
If you and your doctor decide that this therapy is right for you, your doctor will closely monitor your treatment.