Thyroid basics — what you need to know
Reviewed by Dixie Mills, MD, Marcelle Pick, OB/GYN NP and Mary James, ND
You probably know that the thyroid gland is important for weight control and overall
wellness, but many women we talk with aren’t exactly sure what the thyroid does
and how it connects to the way they feel every day.
Low thyroid function, or hypothyroidism, is the most common form of thyroid imbalance.
Symptoms of low thyroid can include fatigue, poor concentration, constipation, weight
gain, skin issues, dry, coarse, or thinning hair or hair loss, and even depression.
Women often call us because they’re experiencing some of these symptoms, but have
been told by their doctors that “everything looks fine.” The fact is, thyroid-related
issues can arise at any age and may not necessarily show up on routine lab tests.
But my doctor says my thyroid results are normal...
In our experience, the ‘normal’ lab ranges for thyroid function that are used in
conventional medicine are not specific enough to identify subclinical problems.
For example, most conventional medicine labs set the ‘normal’ range for TSH as typically
between 0.4 to 4.0 mIU/L, but we like to see TSH stay as close to 2.0 mIU/L as possible;
a higher level can indicate low thyroid function in many women. Ideally, we like
your thyroid levels to stay in the middle of these ranges, rather than at either
end of the extremes. We also often look at a patient’s trends in thyroid function
to see if her levels are creeping up or down over time. And we always pay attention
to the specific symptoms a patient reports.
The good news is that natural thyroid
support is available, and effective.
Though they can vary from lab to lab, typical thyroid ranges in the blood are:
- T4: 4.8–13.2 mcg/dL
- Free T4: 0.9–2 ng/dL
- T3: 80–200 ng/dL
- TSH: 0.4–4.0 mIU/L (if you have no hypothyroid or hyperthyroid
0.3–3.0 mIU/L (if you’re being treated with thyroid hormone)
It’s important to understand the basics so that you’ll know how to best support
your thyroid health at every point in your life.
What does the thyroid do?
Centrally located at the base of the throat, between the brain and rest of the body,
the butterfly-shaped thyroid gland helps maintain overall balance in the body. Its
hormones affect many systems and functions, including:
- Brain development
- Breathing, heart and nervous system function
- Blood cell production
- Muscle and bone strength
- Body temperature
- Menstrual cycles
- Weight gain and loss
- Cholesterol levels
- Skin hydration
Your thyroid helps determine how you metabolize food, how you store and use energy,
how you think, talk, sleep and more! So it makes sense that when your thyroid isn’t
functioning properly, your life can seem significantly off-kilter.
The hormones of the thyroid, thyroxine (T4) and triiodothyronine
(T3), influence the metabolism of each and every cell in our bodies. T3 is the thyroid
hormone that our cells recognize best; it is actually the only biologically active
thyroid hormone in the body. T4 can be thought of as a “preparatory” hormone for
T3; T4 is converted into T3 in the liver and kidneys.
The conversion process of thyroid hormone is a series of events. When T3 and T4
are low in the bloodstream, the part of your brain known as the hypothalamus
— the “command center” for most hormones — sends a message in the form of TRH (thyrotropin-releasing
hormone) to the pituitary gland. Functioning as a sort of “halfway
house” between the brain and the endocrine system, the pituitary gland interprets
the message to secrete more TSH (thyroid-stimulating hormone), which in
turn, prompts your thyroid gland to take up iodine and the amino acid, tyrosine,
to produce more T3 and T4. If your thyroid hormones range too high, the hypothalamic
and pituitary signals become much quieter until your thyroid hormones are in balance
With its elegant system of checks and balances, your body has the natural tendency
to restore thyroid balance. So as long as your hormonal system is fairly well balanced
and your thyroid is properly supported, it will generally move toward its default
“normal” state. This support becomes increasingly important as we age.
Common thyroid imbalances
When your thyroid hormones are too low to support your daily activities, it is known
as hypothyroidism. This can be due to either inadequate
production of T4 in your thyroid gland, or poor conversion of T4 to the more active
T3 hormone. Hypothyroidism can cause severe fatigue and loss of energy, dry skin,
hair changes, general puffiness, constipation, cold intolerance, and more. It can
also increase cholesterol levels and aggravate issues like PMS, menstrual irregularities,
and fibrocystic breasts.
The most common cause of hypothyroidism is an autoimmune disease called Hashimoto’s
thyroiditis. Sometimes women with autoimmune thyroiditis go back and forth between
hyperthyroidism and hypothyroidism.
When the thyroid produces too much thyroid hormone, it is called hyperthyroidism.
Too much thyroid hormone can cause nervousness and anxiety, increased heart rate
or palpitations, breathlessness, diarrhea, insomnia, and depression.
The most common cause of hyperthyroidism is an autoimmune disease called Graves’
disease. Chronic Graves’ disease may cause a person’s eyes to bulge (exophthalmos).
For more on symptoms and causes, see our page on hyperthyroidism.
When someone experiences symptoms of hypothyroidism even though her thyroid test
results are still in the “normal range,” it’s probable that her lab tests are at
either extreme end of the normal range. This is called subclinical hypothyroidism.
Despite having what’s considered “normal” lab test results, people in this category
often feel much better when their thyroid function is enhanced.
Because thyroid imbalances and related disorders typically occur along a continuum,
it’s a good idea to track both your lab work and your symptoms.
Thyroid imbalances are common during hormonal flux
Because the thyroid and ovaries are connected by a feedback loop in the brain, periods
of naturally-shifting hormones can cause disturbances in the thyroid.
Pregnancy. During a healthy pregnancy, estrogen and the
pregnancy hormone hCG (human chorionic gonadotropin) cause increased thyroid hormone
levels in our blood. Because of the natural shifting of hormones during this time,
hypothyroidism and/or hyperthyroidism can occur during or after pregnancy.
Perimenopause. As we begin the journey toward menopause,
estrogen, progesterone, and testosterone are in flux. This fluctuation can affect
messages sent to the brain regarding thyroid hormones. As we produce less estrogen,
thyroid-releasing hormone (TRH) can also slow down, resulting in less available
T3 and T4 for our cells.
Periods of stress. The thyroid gland can be affected when
we’re under stress because of its connection to the adrenal glands (our stress responders).
During periods of chronic stress, the adrenal glands pump out the stress hormones,
cortisol and adrenalin. Although these hormones help our bodies adapt to stress,
they can also inhibit thyroid stimulating hormone (TSH) and the conversion of T4
into the more active thyroid hormone, T3. The result is low thyroid function.
Supporting your thyroid naturally
Given the importance of the thyroid and its responsibilities in your body, it’s
surprisingly easy to provide support in your daily life. Here are the three most
Food for your thyroid. Food plays an essential role in
every day thyroid function. First of all, make a point of eating breakfast every
day, so that your system gets a balanced start. Keep sweets and simple starches
to a minimum and make sure that you get enough protein. Too many carbs and too little
protein can both interfere with the conversion of T4 into T3. Your thyroid also
requires specific nutrients for proper functioning, such as iodine, selenium and
other minerals, tyrosine, and B vitamins. Some of these nutrients are available
in seafood and sea vegetables, as well as poultry, Brazil nuts, mushrooms, legumes,
yogurt, strawberries, and eggs. See our chart on
whole foods to support your thyroid.
Herbs and minerals to support healthy thyroid function.
Herbs like ashwagandha, hops, sage, bacopa monnieri, coleus, and guggul can also
help support thyroid hormone production and balance hormonal signals to the thyroid
gland, thus boosting energy and protecting other functions in the body.
Thyroid-healthy lifestyle changes. You might not expect
that factors like managing stress, taking time for yourself, getting enough sleep,
exercising regularly, and attending to emotional wellness would make a significant
difference when it comes to thyroid health — but they can. So can getting out in
the sun for a bit each day (to help maintain adequate vitamin D levels) and avoiding
exposure to herbicides, pesticides, and cigarette smoke. These steps can also support
your adrenal glands, which are intimately connected to thyroid health.
We’ve made it even easier for you to take care of your thyroid with our
Personal Program for Thyroid Support. With shopping lists of thyroid-supporting
foods, suggestions for appropriate lifestyle changes, and an herbal supplement scientifically
formulated with iodine, selenium, hops, sage, and other thyroid-supporting herbs,
you can cover all the basic physiological needs of your thyroid on a consistent
Comment on this article:
Norman Endocrine Surgery Clinic. 2005. How your thyroid works. URL: http://www.endocrineweb.com/thyfunction.html.
Lombard, J. 2005. Chapter 32. Clinical approaches to hormonal and neuroendocrine
imbalances. Section VI: Neurotransmitters: A functional medicine approach to neuropsychiatry.
In Textbook of Functional Medicine, ed. D. Jones & S. Quinn, 644. Gig Harbor, WA:
Institute for Functional Medicine.
National Endocrine and Metabolic Diseases Information Service. 2008. Pregnancy and
thyroid disease. URL: http://endocrine.niddk.nih.gov/pubs/pregnancy/.
Last Modified Date: 03/29/2012
Reviewed by Dixie Mills, MD and Marcelle Pick, OB/GYN NP