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PubMed This is a summary of 23 peer-reviewed journal articles Updated
Endocrinology

When the Body Slows Down: Symptoms and Emergencies

At a Glance

Hypothyroidism causes the body's metabolism to slow down, leading to fatigue, weight gain, cold intolerance, and brain fog. If left untreated, it can lead to a life-threatening emergency called myxedema coma, marked by severe confusion, slow heart rate, and hypothermia.

Hypothyroidism is often called a “silent” condition because its symptoms can develop so slowly that you might not notice them for months or even years. However, when the body’s metabolism slows down significantly, it affects every organ system, from your brain to your muscles.

Common Signs of Metabolic Slowing

In its early or moderate stages, hypothyroidism causes a general “slowing down” of the body’s processes [1]. You may experience:

  • Cognitive “Brain Fog”: This includes impaired attention, slower speech, and difficulty with memory or executive function [2][3].
  • Metabolic Changes: Unexplained weight gain, feeling cold even in warm rooms (cold intolerance), a slow heart rate (bradycardia), severe dry skin, and hair thinning or loss [4][5][1].
  • Physical Fatigue: A deep, persistent exhaustion that does not improve with rest [1].

Recognizing Severe and Atypical Symptoms

When hypothyroidism remains untreated or becomes severe, it can cause complications that affect the heart and muscles:

  • Cardiovascular Issues: Severe lack of thyroid hormone can cause fluid to build up in the sac around your heart, a condition called pericardial effusion [6]. If too much fluid collects, it can interfere with the heart’s ability to pump [7].
  • Muscle Breakdown: In rare cases, severe hypothyroidism can lead to rhabdomyolysis, where muscle tissue breaks down and releases a protein into the blood that can damage the kidneys [8][9].
  • Neuropsychiatric Changes: Some patients experience “myxedema madness,” which involves acute psychosis, hallucinations, or severe confusion [10][11]. These symptoms are often reversible once thyroid levels are restored [12].

Myxedema Coma: A Medical Emergency

Myxedema coma is the most severe, life-threatening form of hypothyroidism [13]. Despite the name, a patient does not have to be in a full coma to have this condition. It is a state of “decompensation” where the body can no longer maintain its basic functions [14].

Warning Signs of Myxedema Coma:

  1. Altered Mental Status: Significant confusion, extreme lethargy, or loss of consciousness [15].
  2. Hypothermia: A dangerously low body temperature, often below 95°F (35°C) [4].
  3. Slow Heart Rate and Low Blood Pressure: The heart cannot maintain its usual pace or pressure [4][16].

Common Triggers: This emergency is often triggered by an external stressor in someone who already has untreated or poorly managed hypothyroidism. Triggers include serious infections (like a UTI or the flu), exposure to extreme cold, or abruptly stopping thyroid medication [17][18].

If you suspect someone is experiencing these symptoms, call 911 or your local emergency number immediately [19]. Do not attempt to drive them to the emergency room.

Is it My Thyroid, Depression, or Perimenopause?

Many symptoms of hypothyroidism—such as low mood, fatigue, and weight changes—overlap with clinical depression or the transition to menopause [20][21].

  • Clinical Differentiation: While depression may cause mental “slowing,” hypothyroidism often includes physical signs like a very slow pulse, low body temperature, and dry skin [22][5].
  • Lab Testing: Because these conditions look so similar, doctors rely on blood tests (TSH and Free T4) to determine if the thyroid is the primary cause of the symptoms [23]. It is also highly recommended that patients checking into psychiatry or gynecology for antidepressants or HRT have their TSH tested first to rule out the thyroid. It is also possible to have both hypothyroidism and depression simultaneously [21].

Common questions in this guide

Can hypothyroidism cause brain fog and memory issues?
Yes, hypothyroidism can cause cognitive issues commonly referred to as "brain fog." This includes impaired attention, slower speech, and difficulty with memory or executive function.
What is a myxedema coma?
Myxedema coma is a life-threatening medical emergency caused by severely low thyroid hormone levels. Warning signs include significant confusion, a dangerously low body temperature, and a slow heart rate. It requires immediate emergency medical care.
How do I know if my symptoms are from hypothyroidism, depression, or menopause?
While fatigue and low mood are common in depression and perimenopause, hypothyroidism often includes specific physical signs like a very slow pulse, feeling cold, and dry skin. A TSH blood test is the best way to determine if your thyroid is the root cause.
Can severe hypothyroidism affect my heart?
Yes, a severe lack of thyroid hormone can cause fluid to build up in the sac around your heart, a condition called pericardial effusion. If too much fluid collects, it can cause shortness of breath and interfere with your heart's ability to pump.
What does it mean if I have severe muscle pain and dark urine with hypothyroidism?
Rarely, severe hypothyroidism can lead to rhabdomyolysis, a condition where muscle tissue breaks down. This can cause severe muscle pain and very dark urine, and it requires medical evaluation to prevent kidney damage.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Are my symptoms—like low mood and fatigue—consistent with my thyroid levels, or should we also consider depression or perimenopause?
  2. 2.If I experience severe muscle pain or very dark urine, could that be rhabdomyolysis related to my thyroid?
  3. 3.Could the shortness of breath I’m feeling be related to fluid around my heart (pericardial effusion)?
  4. 4.If I get a serious infection like the flu, do I need to adjust how I monitor my thyroid symptoms to avoid Myxedema Coma?
  5. 5.What should my family or caregivers look for if my mental state changes?
  6. 6.Can we check my TSH level before you prescribe an antidepressant or hormone replacement therapy (HRT)?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (23)
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    Shared Decisionmaking in the Treatment of Hypothyroidism.

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    Visual Hallucinations and Cognitive Impairment as the Initial Presentation of Severe Hypothyroidism in an Elderly Patient: A Case Report.

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    Older woman presenting with recurrent falls: An unusual manifestation of hypothyroidism.

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    Rare Presentation of Cardiac Tamponade in a Patient With Subclinical Hypothyroidism.

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    Myxedema coma with cardiac tamponade and severe cardiomyopathy.

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    All That Glitters Like Gold Is Not Good: A Rare Constellation of Pericardial Effusion Without Cardiac Tamponade and Biochemical Myopathy in Hypothyroidism.

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    Handwriting characteristics in patients with overt autoimmune hypothyroidism: a prospective case-control study.

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This page provides information on hypothyroidism symptoms and emergencies for educational purposes only. If you suspect myxedema coma or a severe medical complication, call 911 or seek emergency medical care immediately.

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