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Can thyroid happen suddenly?

Thyroid conditions like hypothyroidism and hyperthyroidism can sometimes seem to come on suddenly, but in most cases they develop gradually over time. There are a few scenarios in which thyroid problems can appear to occur more acutely:

Postpartum thyroiditis

Postpartum thyroiditis is a condition that can cause thyroid problems shortly after giving birth. It is estimated to affect around 5-10% of women within a year after delivery. The symptoms are caused by inflammation of the thyroid gland and usually follow a certain pattern:

  • 1-4 months postpartum: Thyroid hormone production is high, leading to symptoms of hyperthyroidism like anxiety, insomnia, heart palpitations, etc.
  • 4-8 months postpartum: The thyroid’s hormone production declines, leading to hypothyroid symptoms like fatigue, weight gain, dry skin, etc.
  • 8-12 months postpartum: Thyroid function often returns to normal, but in some women hypothyroidism remains permanent and requires lifelong treatment.

So in postpartum thyroiditis, a woman may suddenly develop hyperthyroid or hypothyroid symptoms within the first year after giving birth, even if her thyroid function was normal during pregnancy. The fluctuations reflect the autoimmune inflammation causing temporary thyroid malfunction.


There are a few other types of thyroiditis—inflammation of the thyroid—that can also cause relatively abrupt changes in thyroid hormone levels:

  • Subacute thyroiditis: Often follows a viral infection and causes painful thyroid gland swelling and temporary hyperthyroidism followed by hypothyroidism before the thyroid recovers.
  • Acute (suppurative) thyroiditis: A bacterial thyroid infection leading to thyroid pain, fever, and hyperthyroidism.
  • Silent (painless) thyroiditis: Usually temporary hypothyroidism with few if any symptoms. May follow pregnancy or a viral infection.
  • Drug-induced thyroiditis: Certain medications like interferon-alpha, interleukin-2, amiodarone, lithium, interleukin-2, etc. can inflame the thyroid and affect its hormone production.

In these types of thyroiditis, a person may have normal thyroid function one week and overt hypothyroidism or hyperthyroidism the next week due to the inflammation. Symptoms appear suddenly once the drugs are started or the viral trigger occurs.

Post-surgical hypothyroidism

Patients who have surgery to remove part or all of their thyroid gland can develop acute hypothyroidism within days after the operation. This occurs because the remaining thyroid tissue is suddenly not enough to meet the body’s hormone needs. Patients may experience profound fatigue, constipation, weight gain, and other hypothyroid symptoms shortly after surgery before thyroid hormone replacement is optimized.

Thyroid storm

Thyroid storm is a rare, life-threatening condition caused by untreated severe hyperthyroidism. It can be abruptly triggered by stress, surgery, trauma, or certain medications. Symptoms appear suddenly and include high fever, vomiting, diarrhea, dehydration, rapid heart rate, and blood pressure changes. Thyroid storm requires emergency treatment to prevent shock, organ failure, and potential death.

Iodine overload

Consuming very high amounts of iodine can damage the thyroid and impair its function. This could occur with certain medications like amiodarone, contrast dyes used in some X-ray procedures, dietary supplements like kelp tablets, or eating lots of seaweed. Too much iodine can lead to either hypothyroidism or hyperthyroidism, causing symptoms to develop suddenly.


The increased hormone production demands during pregnancy can unmask mild or borderline thyroid problems. Symptoms of hypothyroidism like fatigue, constipation, dry skin may suddenly appear in a pregnant woman whose thyroid function was marginal prior to pregnancy but is no longer adequate. Hyperthyroidism can also arise abruptly during pregnancy.

Radiation exposure

Significant radiation exposure from sources like nuclear accidents, cancer treatments, or repeated medical imaging can damage the thyroid gland and cause acute hypothyroidism within days to months of exposure. This occurred in many children affected by the Chernobyl nuclear accident.

Hashimoto’s thyroiditis

Hashimoto’s thyroiditis is an autoimmune disorder and the most common cause of hypothyroidism. It causes gradual destruction of the thyroid gland over months to years, leading to progressively worsening hypothyroidism. But some people with Hashimoto’s report periods where their symptoms seem to flare-up and become much more noticeable before settling down again. This may reflect episodes of more intense autoimmune activity against the thyroid.

Graves’ disease

Graves’ disease is the most common cause of hyperthyroidism. Like Hashimoto’s, it is an autoimmune disorder but it causes the thyroid to produce excess hormones instead of too few. Graves’ disease usually starts slowly but symptoms can worsen suddenly, particularly after emotional or physical stress. Periods of more intense antibodies stimulating the thyroid may account for these acute symptom flares.

Thyroid function tests

While symptoms may sometimes appear suddenly, laboratory tests show that thyroid function declines or increases more gradually over time. The typical pattern is:

  • TSH: Starts to increase (hypothyroidism) or decrease (hyperthyroidism)
  • T4: Decreases (hypothyroidism) or increases (hyperthyroidism)
  • T3: Decreases (hypothyroidism) or increases (hyperthyroidism)
  • Thyroid antibodies: May become detectable or begin rising

So blood tests can help determine if thyroid changes are truly acute or if they have been evolving subclinically over a longer period.


In summary, thyroid conditions like hypothyroidism and hyperthyroidism often develop slowly, but there are circumstances in which symptoms and lab changes appear more suddenly:

  • Postpartum thyroiditis in the first year after giving birth
  • Episodes of thyroiditis caused by viruses, bacteria, or medications
  • Immediately after thyroid surgery
  • Thyroid storm triggered by stress in severe hyperthyroidism
  • Excess iodine consumption
  • Symptom flares in Hashimoto’s or Graves’ disease
  • Radiation exposure
  • Undiagnosed thyroid dysfunction unmasked by pregnancy

However, even when symptoms seem to come on quickly, blood tests will usually show more gradual changes in thyroid hormone levels. So while thyroid conditions may sometimes appear sudden, they are generally evolving processes that eventually cross the threshold into overt hypothyroidism or hyperthyroidism.

Frequently Asked Questions

Can you suddenly develop an underactive thyroid?

It is uncommon for hypothyroidism to appear suddenly, but possible scenarios include postpartum thyroiditis after giving birth, thyroiditis from viruses/medications, destruction after radioactive iodine treatment for hyperthyroidism, and surgical removal of part or all of the thyroid gland. Autoimmune Hashimoto’s thyroiditis causes gradual thyroid failure over months/years, but symptomatic flares can occur.

What causes your thyroid to stop working suddenly?

Viral or bacterial thyroiditis, high iodine intake, radiation exposure, medications, pregnancy, and postpartum thyroiditis can suddenly impair thyroid function and cause hypothyroidism. Most cases of thyroid failure are due to the gradual autoimmune destruction of Hashimoto’s thyroiditis however.

Can hyperthyroidism happen overnight?

Hyperthyroidism does not typically develop overnight. Grave’s disease is the most common cause and symptoms worsen gradually over weeks to months. But patients with unrecognized mild Graves’ can experience acute worsening of symptoms called thyroid storm, which requires emergency treatment.

What are the symptoms of a thyroid storm?

Signs of a thyroid storm include high fever, diarrhea, vomiting, dehydration, confusion, rapid heart rate, heart arrhythmias, high or low blood pressure, and sometimes loss of consciousness. It results from a sudden spike in thyroid hormone levels in someone with untreated hyperthyroidism.

Can thyroid issues appear suddenly?

Thyroid problems more typically develop slowly over time. But symptoms can seem to appear suddenly in postpartum thyroiditis after giving birth, thyroiditis caused by infections/medications, iodine excess, after thyroid surgery, symptom flares in Graves’/Hashimoto’s, radiation exposure, pregnancy, and thyroid storm.

Can hypothyroidism be mistaken for anxiety?

Yes, anxiety is a common symptom of hypothyroidism. Other overlapping symptoms include fatigue, depression, muscle cramps, insomnia, hair loss, weight changes, and more. Hypothyroidism should be ruled out in anyone with unexplained anxiety symptoms.

Why is my thyroid fluctuating so much?

Frequent fluctuations in thyroid levels can be seen in thyroiditis caused by autoimmune problems, infections, or medications. Hashimoto’s and Graves’ disease can also cause thyroid levels to be unstable. Optimal treatment helps stabilize thyroid function.

Can thyroid nodules appear suddenly?

Most thyroid nodules grow slowly over months to years. They may not be noticed until large enough to feel as a neck lump. But some nodules can enlarge more rapidly over days to weeks, in which case they would seem to appear suddenly.

Can hyperthyroidism make you feel weak and tired?

Yes, surprisingly hyperthyroidism can cause fatigue along with muscle weakness, despite its reputation for causing symptoms like anxiety, insomnia, and rapid heart rate. The fatigue may be due to underlying autoimmune inflammation in Graves’ disease.

Key Takeaways

  • Postpartum thyroiditis, thyroiditis from infections/medications, high iodine intake, radiation exposure, thyroid surgery, symptom flares in autoimmune thyroid disease, pregnancy, and thyroid storm can all cause thyroid problems to appear suddenly.
  • However, blood tests typically show more gradual changes in TSH and thyroid hormone levels over time rather than abrupt shifts.
  • Symptoms may seem to come on quickly even when the underlying thyroid condition has been developing for months to years.
  • Hypothyroidism and hyperthyroidism arising suddenly requires prompt diagnosis and treatment to relieve symptoms and prevent complications.