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Thyroid disorders include hypothyroidism (underactive thyroid, ICD-10 E03.9) and hyperthyroidism (overactive thyroid, ICD-10 E05.90), and they affect roughly 20 million Americans — about 60% of whom are unaware they have a problem (American Thyroid Association, 2024). The thyroid is a small gland in the front of the neck that controls how every cell in the body uses energy. When it under- or over-produces hormone, it shows up as fatigue, unexplained weight change, mood shifts, heart-rate changes, and temperature intolerance. The first-line test is a TSH (thyroid-stimulating hormone) level — the American Thyroid Association considers the normal range roughly 0.5 to 4.0 mIU/L (ATA 2014 hypothyroidism guideline). Discuss test selection and review with your provider. Confirm collection location, availability, follow-up format and coverage; this page does not attest onsite thyroid testing.
Hypothyroidism — Underactive Thyroid
Hypothyroidism is the most common thyroid disorder in the United States. The most common cause is Hashimoto's thyroiditis — an autoimmune condition in which the body's immune system gradually damages the thyroid (NIDDK, 2024). When the thyroid does not make enough hormone, the entire body slows down. Patients describe waking up tired even after 8 hours of sleep, dry skin and brittle hair, slow weight gain over months, cold intolerance, constipation, and a mental sluggishness that is hard to put into words. In women, irregular or heavy periods are common.
- Symptoms — fatigue, cold intolerance, weight gain, dry skin, hair thinning, constipation, low mood, slowed thinking
- First-line test — TSH level (normal range approximately 0.5 to 4.0 mIU/L per ATA 2014)
- Confirmatory tests — Free T4, sometimes Free T3, and anti-TPO antibodies if Hashimoto's is suspected
- Treatment — thyroid hormone replacement, dosed by weight and TSH, with repeat labs at 6 to 8 weeks after starting or adjusting
- Long-term — most patients reach a stable dose and are monitored once a year by TSH
- Outside endocrinology assessment may be indicated for difficult dosing, large goiter or pregnancy; confirm acceptance, access and result ownership
Hyperthyroidism — Overactive Thyroid
Hyperthyroidism is less common than hypothyroidism but more dramatic in presentation. The most common cause in the United States is Graves' disease, an autoimmune condition that drives the thyroid to overproduce hormone (Endocrine Society 2016 hyperthyroidism guideline). Patients often describe a heart that races at rest, unintentional weight loss despite a normal or increased appetite, anxiety, irritability, heat intolerance and sweating, hand tremor, and difficulty sleeping. In older adults, atrial fibrillation can be the presenting sign.
- Symptoms — palpitations, anxiety, weight loss despite eating, heat intolerance, tremor, insomnia, eye prominence in Graves'
- First-line test — TSH (suppressed, often below 0.1 mIU/L) with elevated Free T4 and Free T3
- Confirmatory tests — TSI (thyroid-stimulating immunoglobulin) for Graves', thyroid uptake scan for nodular disease
- Treatment options to discuss with endocrinology — antithyroid medications, radioactive iodine or surgery; confirm the qualified outside setting, availability, costs and responsible provider
- Cardiac safety — heart-rate control is the first priority when palpitations or atrial fibrillation are present
- Eye involvement — outside ophthalmology assessment may be indicated for suspected Graves' eye disease; confirm acceptance, access and completed handoff
Who Should Be Screened for Thyroid Disease
The U.S. Preventive Services Task Force concluded in 2015 that current evidence is insufficient to recommend universal screening for asymptomatic adults (USPSTF 2015 thyroid statement). However, both the American Thyroid Association and the American Association of Clinical Endocrinologists recommend checking TSH when symptoms suggest thyroid disease, in adults over 60, in women planning pregnancy, in patients with autoimmune disease or strong family history, and in anyone with a goiter (visible neck swelling) or thyroid nodule.
- Adults with symptoms — fatigue, weight change, mood changes, heart-rate changes, temperature intolerance
- Women planning pregnancy or in the first trimester — uncontrolled thyroid disease affects fetal development
- Adults over 60 — symptoms are easy to attribute to aging and can be missed
- Patients with autoimmune disease — type 1 diabetes, celiac, lupus, rheumatoid arthritis increase risk
- Strong family history of thyroid disease — siblings and parents are the highest-risk relatives
- Visible neck swelling or a palpable nodule — needs ultrasound and possibly biopsy
Thyroid and Pregnancy
Thyroid hormone is essential for fetal brain development in the first trimester, when the baby relies entirely on the mother's supply. The American Thyroid Association's 2017 pregnancy guideline recommends a TSH target below 2.5 mIU/L in the first trimester for women already on thyroid hormone replacement, and prompt evaluation for any woman with new symptoms or known thyroid disease who is planning pregnancy or newly pregnant. Dosing typically needs to increase by 20% to 30% during pregnancy.
- Preconception — confirm TSH is in target range before conception when possible
- First trimester — TSH target below 2.5 mIU/L in patients on hormone replacement (ATA 2017)
- Dose adjustment — most patients on hormone replacement need a 20% to 30% dose increase
- Postpartum thyroiditis — about 5% to 10% of women develop transient thyroid dysfunction in the first year after delivery
- Discuss coordination between obstetric and thyroid care providers on tests and dosing; confirm who accepts responsibility for results and treatment changes
Thyroid and Weight — An Honest Conversation
One of the most common reasons patients ask for a thyroid test is unexplained weight gain. The honest medical reality is more limited than the public narrative suggests. When hypothyroidism is genuinely present and untreated, modest weight gain — typically 5 to 10 pounds of water and slowed metabolism — is real, and weight tends to normalize after treatment. However, thyroid hormone replacement is not a weight-loss medication. Using it in a patient with a normal TSH does not help with weight loss and carries real cardiac and bone-density risks (American Association of Clinical Endocrinologists position statement).
- If TSH is elevated and symptoms fit — treatment may restore a small amount of weight, energy, and metabolism
- If TSH is normal — thyroid medication is not appropriate for weight loss
- Medical weight management — discuss clinically appropriate options and confirm available resources
- Common other causes of weight gain to evaluate — sleep, insulin resistance, mood, medication side effects, perimenopause
Topics to Discuss for an Individual Thyroid Assessment
A thyroid assessment can review symptoms, medications and supplements, family history, a neck examination and a testing plan. Confirm appointment duration and whether blood collection is available onsite or arranged externally.
- History — current symptoms, family history, medications, supplements that affect the thyroid (biotin, iodine, certain mood-stabilizing medication classes)
- Physical exam — neck palpation for goiter or nodule, pulse, blood pressure, reflexes, skin and hair
- A provider may select TSH first, with free T4, free T3 or antibodies based on initial findings; confirm test access and result ownership
- Discuss what results may mean, whether repeat testing or treatment is indicated, and who will review results; confirm access and follow-up
- Follow-up — typically 6 to 8 weeks after starting or changing thyroid hormone replacement, then annually when stable
Insurance and Language Support to Confirm
Confirm provider availability, test location, referrals, costs and insurance coverage before scheduling. Testing or specialist care may take place outside Viva; acceptance and timing require confirmation.
- Coverage — confirm the individual plan and any external provider before scheduling
- Costs — request a current estimate for visits, tests and outside services
- Language support — confirm visit, written information and portal resources
- Appointments — confirm current availability before scheduling
- Follow-up format — confirm whether an in-person or remote visit is available and clinically suitable
Sources
- American Thyroid Association — Patient Information & Guidelines — American Thyroid Association
- Hypothyroidism (Underactive Thyroid) — NIDDK — National Institute of Diabetes and Digestive and Kidney Diseases (NIH)
- USPSTF — Thyroid Dysfunction: Screening (2015) — U.S. Preventive Services Task Force
- Endocrine Society — Hyperthyroidism and Other Causes of Thyrotoxicosis Guideline — Endocrine Society
Frequently Asked Questions
What are the symptoms of hypothyroidism versus hyperthyroidism?
Hypothyroidism (underactive thyroid) slows the body down: fatigue, weight gain, cold intolerance, dry skin, hair thinning, constipation, low mood, and slowed thinking. Hyperthyroidism (overactive thyroid) speeds it up: palpitations, weight loss despite a normal or larger appetite, heat intolerance, sweating, tremor, anxiety, and insomnia. Symptoms overlap with many other conditions, which is why a TSH blood test is the right first step rather than guessing from symptoms alone.
Who should be screened for thyroid disease?
The American Thyroid Association recommends a TSH test in adults with any of the symptoms above, in women planning pregnancy or newly pregnant, in adults over 60, in anyone with an autoimmune condition or strong family history of thyroid disease, and in anyone with a goiter or palpable nodule. The USPSTF concluded in 2015 that universal screening of asymptomatic adults is not currently recommended, but symptom-driven testing is well-established.
How often should I get my TSH tested?
After starting or adjusting thyroid hormone replacement, TSH is rechecked at 6 to 8 weeks. Once stable on a dose, most patients need a TSH once a year. In pregnancy, testing is more frequent — typically each trimester and 6 weeks postpartum. For patients with thyroid antibodies but normal TSH, annual or biannual monitoring is reasonable. A provider can set an individual cadence based on results and risk; confirm test access and who reviews results.
What should I expect from treatment?
For hypothyroidism, thyroid hormone replacement is taken daily, usually first thing in the morning on an empty stomach, and most patients reach a stable dose within 2 to 3 months. Symptoms improve gradually — energy and mood often improve in the first month; hair, skin, and weight changes can take several months. For hyperthyroidism, treatment depends on the cause and may involve antithyroid medications, radioactive iodine, or surgery, coordinated with endocrinology.
Does the thyroid affect weight, and can thyroid medication help me lose weight?
Thyroid hormone affects metabolism, so untreated hypothyroidism can cause a modest weight gain — typically 5 to 10 pounds of water and slowed metabolism — that tends to normalize after treatment. However, thyroid hormone replacement is not a weight-loss medication. Using it in a patient with a normal TSH does not produce weight loss and carries real risks to the heart and bones. If weight is your concern and your TSH is normal, discuss weight assessment and confirm available support.
I am planning pregnancy. Should I have my thyroid checked?
Yes. Thyroid hormone is essential for fetal brain development in the first trimester. The American Thyroid Association recommends a TSH check before conception when possible. Women already on thyroid hormone replacement typically need a 20% to 30% dose increase during pregnancy, and TSH should be kept below 2.5 mIU/L in the first trimester (ATA 2017 pregnancy guideline). Discuss coordination with your obstetric and thyroid care providers; confirm who is responsible for results and treatment changes.
What is Hashimoto's and what is Graves' disease?
Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States — an autoimmune condition in which the immune system gradually damages the thyroid. It is diagnosed by anti-TPO antibodies and is treated with thyroid hormone replacement. Graves' disease is the most common cause of hyperthyroidism — also autoimmune, but in this case the antibodies stimulate the thyroid to overproduce hormone. It is treated with antithyroid medications, radioactive iodine, or surgery, depending on severity and patient preference.
Does insurance cover thyroid testing and treatment?
Confirm provider availability, test location, referrals, costs and insurance coverage before scheduling. Testing or specialist care may take place outside Viva; acceptance and timing require confirmation.
Do you offer bilingual care?
Ask which English or Spanish visit and written education resources are available. Confirm remote care and portal support separately.
Can I be seen by telehealth for thyroid follow-up?
Follow-up format — confirm whether an in-person or remote visit is available and clinically suitable