Is hair loss a common side effect of thyroid cancer treatment?

Hair loss is not typical with the most common thyroid cancer treatments, which are surgery and radioactive iodine (RAI). Hair loss is more commonly linked to chemotherapy and radiation to the head, which most people with differentiated thyroid cancer do not receive. Chemotherapy and head radiation can damage fast‑growing hair cells and lead to temporary or sometimes permanent hair loss. ^[1] Hair loss can also occur from other factors such as low thyroid hormone levels (hypothyroidism), which is sometimes seen during or after treatment, and from some medications or nutritional issues. ^{[1] [2]}

Which thyroid cancer treatments can cause hair loss?

• Surgery (thyroidectomy)

  • Surgery itself does not cause hair loss. However, if thyroid hormone levels drop after surgery (hypothyroidism) or during dose adjustments, diffuse hair shedding may occur and usually improves once levels are corrected. Low thyroid function is a known contributor to hair loss. ^[2]

• Radioactive iodine (RAI)

  • RAI does not usually cause scalp hair loss. If hypothyroidism is induced to prepare for RAI (by stopping thyroid hormone) or if hormone levels are not well balanced afterward, temporary shedding may occur until levels are restored. Low thyroid function can contribute to hair loss. ^[2]

• External beam radiation therapy (EBRT) to the neck or head

  • Radiation directed at the head commonly causes hair loss in the treated area because it affects hair follicles; regrowth varies based on dose and field. ^[1]

• Chemotherapy or certain targeted therapies

  • Chemotherapy frequently causes hair loss across the scalp and sometimes body hair because it targets fast‑dividing cells, including hair follicles. ^[1]
  • Some targeted therapies and immunotherapies can also lead to thinning or hair changes, though the risk is generally lower compared with classic chemotherapy. ^{[3] [4]}

Other reasons hair may thin during thyroid cancer care

• Thyroid hormone imbalance

  • Both low and high thyroid hormone states can contribute to shedding; correcting levels typically improves hair over time. ^{[5] [6]}

• Stress, nutrition, and other health conditions

  • Stress, iron or vitamin deficiencies, and certain hairstyles or products can contribute to shedding and thinning. A dermatology evaluation can help identify the cause and plan treatment. ^{[1] [2]}

What to expect if hair loss happens

• Timing and pattern

  • With chemotherapy, shedding often begins 1–3 weeks after the first cycle and can include scalp, eyebrows, eyelashes, and body hair. ^[1]
  • With radiation to the head, hair loss occurs in the irradiated field; regrowth may be incomplete depending on dose. ^[1]
  • With thyroid hormone imbalance, shedding is typically diffuse and gradual; improvement follows stabilization of hormone levels. ^{[5] [6]}

• Regrowth

  • After chemotherapy, hair usually regrows within months, though color or texture can change. ^[1]
  • After radiation to the head, regrowth depends on the dose; sometimes it may be thinner or not fully return. ^[1]

How to manage and prevent hair loss

Medical and preventive strategies

• Optimize thyroid levels

  • Work with your clinician to keep thyroid hormone levels in range; this often reduces shedding related to thyroid imbalance. ^{[5] [6]}

• Scalp cooling (cold caps) during chemotherapy

  • Cooling the scalp during infusions can reduce chemotherapy‑related hair loss by putting follicles into a resting state. This option is not used with RAI or surgery. ^{[2] [7]}

• Dermatology support

  • An oncodermatology or dermatology consultation can help diagnose the cause, treat scalp symptoms, and discuss preventive and cosmetic strategies. Programs dedicated to managing treatment‑related hair issues can improve quality of life. ^{[4] [8] [9]}

Gentle hair and scalp care

• Use mild, fragrance‑free shampoos; wash less frequently and with lukewarm water to reduce irritation. ^[2]
• Pat hair dry, avoid high‑heat styling, tight hairstyles, bleaching, or harsh treatments. ^[2]
• Brush gently with a soft‑bristle brush and consider shorter hairstyles to make thinning less noticeable. ^{[10] [2]}

Sun and temperature protection

• Protect the scalp from sunburn with hats, scarves, and sunscreen when outdoors; keep the scalp warm in cold weather. ^[2]

Camouflage and cosmetic options

• Consider wigs or toppers; visiting a stylist before significant shedding helps match color and style. ^[11]
• Use powders, fibers, and sprays designed to conceal thinning areas for a natural look. ^[10]

When to seek further evaluation

• If hair loss is sudden, patchy, associated with scalp pain, redness, or scarring, or persists despite stable thyroid labs, a dermatology assessment is advisable to rule out other causes and to discuss treatments. ^{[2] [4]}

Key takeaways

• Most people treated for thyroid cancer with surgery and RAI do not experience significant hair loss. Hair loss is more commonly linked to chemotherapy and radiation to the head. ^[1]
• Low thyroid hormone levels, which can occur around treatment, may also cause temporary shedding that improves when levels are corrected. ^[2]
• Practical steps optimizing thyroid levels, considering scalp cooling during chemotherapy, gentle hair care, scalp protection, and cosmetic aids can help prevent and manage hair loss and improve confidence during treatment. ^{[2] [10] [11] [4]}