Hormonal Health
Thyroid Disorders: Hypothyroidism, Hyperthyroidism, and Hashimoto's
Haute MD Editorial Team
The thyroid gland — a butterfly-shaped gland at the base of the neck — produces hormones (T4 and T3) that regulate metabolism, energy production, heart rate, body temperature, and virtually every organ system. Thyroid disorders are among the most common endocrine conditions, affecting an estimated 20 million Americans. Hypothyroidism (underactive thyroid) is the most common, affecting 5% of the US population with subclinical disease affecting an additional 5-10%. Hyperthyroidism (overactive thyroid) is less common but produces significant symptoms. Both are highly treatable — the challenge is often accurate diagnosis, as symptoms overlap with many other conditions.
Hypothyroidism — causes, symptoms, and treatment
The most common cause of hypothyroidism in developed countries is Hashimoto's thyroiditis — an autoimmune condition in which the immune system attacks the thyroid gland, gradually destroying its function. Other causes include thyroid surgery, radioactive iodine treatment, and iodine deficiency. Symptoms — fatigue, weight gain despite unchanged diet, constipation, cold intolerance, dry skin and hair, hair loss, depression, cognitive slowness ("brain fog"), and elevated cholesterol. Treatment — levothyroxine (synthetic T4) is the standard treatment. Some patients feel better on combination T4/T3 therapy (levothyroxine plus liothyronine) — discuss with your physician if you have persistent symptoms on T4 alone.
Complete thyroid testing — why TSH alone is insufficient
Standard practice is to screen with TSH (thyroid-stimulating hormone) alone. While TSH is a sensitive screening test, it does not tell the complete story. Free T4 (the storage form of thyroid hormone) and free T3 (the active form that enters cells) add critical information — particularly for patients who have normal TSH but continue to feel symptomatic. TPO antibodies (thyroid peroxidase antibodies) diagnose Hashimoto's thyroiditis before TSH becomes abnormal. Thyroglobulin antibodies are also relevant. A complete panel — TSH, free T4, free T3, TPO antibodies, thyroglobulin antibodies — provides a full picture that TSH alone cannot.
Hyperthyroidism — Graves' disease and treatment options
Hyperthyroidism is most commonly caused by Graves' disease — an autoimmune condition that stimulates the thyroid to overproduce hormone. Symptoms — rapid heartbeat, weight loss despite increased appetite, heat intolerance, excessive sweating, anxiety, tremor, diarrhea, and in Graves' disease specifically, eye changes (exophthalmos — bulging eyes). Treatment options — antithyroid medications (methimazole, propylthiouracil) to reduce hormone production, radioactive iodine (RAI) to permanently reduce thyroid function (requires subsequent lifelong thyroid hormone replacement), or thyroid surgery. Beta-blockers control symptoms (heart rate, tremor) while the primary treatment takes effect.
Frequently Asked Questions
What TSH level is normal?
Standard laboratory "normal" ranges for TSH are approximately 0.4-4.5 mIU/L. However, many functional and integrative medicine practitioners consider an optimal TSH range of 1.0-2.5 mIU/L for people who are symptomatic. A TSH at the high end of "normal" (3.0-4.5) in someone with significant fatigue, weight gain, and hair loss may warrant a trial of treatment — discuss this with your physician. There is no universal consensus on optimal TSH range.
Does hypothyroidism cause weight gain?
Yes, but typically modest weight gain — usually 5-10 lbs from fluid retention and metabolic slowing. Hypothyroidism alone rarely causes obesity. Treating hypothyroidism corrects the hormonal imbalance but does not automatically produce significant weight loss in most patients. Additional weight management strategies are usually required alongside thyroid treatment.
What is subclinical hypothyroidism?
Subclinical hypothyroidism is defined as an elevated TSH with normal free T4 — suggesting the pituitary is working harder to maintain thyroid hormone production. Whether to treat is controversial and depends on the degree of TSH elevation, symptoms, antibody status (Hashimoto's), age, and cardiovascular risk. Women with TPO antibodies and TSH above 4.5-10 generally benefit from treatment. Discuss individualized decisions with a knowledgeable physician.
Can thyroid disease cause hair loss?
Yes. Both hypothyroidism and hyperthyroidism can cause diffuse hair loss (telogen effluvium). Hair loss typically improves with treatment of the underlying thyroid condition, though recovery takes 3-6 months after thyroid function is normalized. If hair loss persists after thyroid function is well-controlled, evaluate for other causes (iron deficiency, FPHL, nutritional deficiencies).
Get Help Now
Speak with a Haute MD Internal Medicine physician
Are you a Internal Medicine physician?
Join Haute MD Network and have your profile featured alongside these answers.
Apply for the NetworkRelated Guides
Guide · HORMONAL-HEALTH
Hormone Optimization: What It Is and Who Benefits
Hormone optimization uses evidence-based testing and therapy to restore optimal hormone levels. Learn who benefits, what's tested, and what treatment looks like.
Read GuideGuide · HORMONAL-HEALTH
Hormone Testing: What to Test and How to Interpret Results
Standard hormone panels miss critical markers. Learn what comprehensive hormone testing includes, how to interpret results, and how to find a physician who tests correctly.
Read Guide