What are the symptoms and treatment of hypothyroidism?

Symptoms of Hypothyroidism

The common symptoms of hypothyroidism include fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, muscle cramps, voice changes, intellectual slowness, and insomnia. 1 These symptoms result from a decreased metabolic rate due to insufficient thyroid hormone.

Clinical Presentation

Hypothyroidism presents with a constellation of symptoms that can vary in severity:

Common Physical Symptoms

• Fatigue and lethargy
• Weight gain despite no change in diet
• Cold intolerance
• Constipation
• Dry skin and hair
• Hair loss
• Muscle cramps and weakness
• Voice changes (hoarseness)
• Edema (swelling)
• Bradycardia (slow heart rate)

Neuropsychiatric Symptoms

• Mental slowness and poor concentration
• Depression
• Irritability
• Memory problems
• Insomnia

Advanced Symptoms

With progression of untreated hypothyroidism, more severe manifestations can develop:

• Myxedema (severe swelling of tissues)
• Myxedema coma (life-threatening condition) 1

Laboratory Diagnosis

Diagnosis is primarily based on blood tests:

• Elevated thyroid-stimulating hormone (TSH) with low free T4 indicates overt primary hypothyroidism 1
• Subclinical hypothyroidism is identified by elevated TSH with normal free T4 levels
• Additional testing for thyroid antibodies such as thyroid peroxidase (TPO) antibody may be warranted to identify autoimmune causes 1

Common Causes

The most common causes of hypothyroidism include:

1. Hashimoto's thyroiditis (chronic autoimmune thyroiditis) - most frequent cause in industrialized nations 1
2. Iodine deficiency - most common cause worldwide 1
3. Iatrogenic causes:
   • Post-thyroidectomy
   • Radioactive iodine therapy
   • Medications
4. Subacute thyroiditis - can lead to transient or permanent hypothyroidism 1

Treatment Approach

Treatment involves thyroid hormone replacement therapy:

1. Levothyroxine (T4) is the standard treatment:

   • Starting dose typically 1.5-1.8 mcg/kg/day for most adults 2
   • Lower starting doses (12.5-50 mcg/day) for elderly patients or those with cardiac disease 3
   • Goal is to normalize TSH levels (typically 0.4-4.5 mIU/L) 4

2. Monitoring:

   • TSH and free T4 levels should be checked 6-8 weeks after starting therapy or changing doses 4
   • Once stable, monitoring every 6-12 months is recommended 4

3. Special considerations:

   • Pregnancy requires dose adjustments (typically 30% increase) 3
   • Elderly patients need more cautious dosing due to increased cardiac risk 3
   • Patients with adrenal insufficiency require corticosteroid treatment before starting thyroid hormone replacement to prevent adrenal crisis 4

Complications of Untreated Hypothyroidism

Failure to treat hypothyroidism can lead to:

• Increased cardiovascular disease risk
• Higher mortality
• Cognitive impairment
• Infertility or pregnancy complications
• Myxedema coma (rare but life-threatening) 5

Important Pitfalls to Avoid

1. Misdiagnosis: Symptoms of hypothyroidism are nonspecific and may overlap with other conditions, making diagnosis challenging without laboratory confirmation 6

2. Inadequate treatment: Nearly one-third of treated patients still experience symptoms despite normalized TSH levels 7

3. Overtreatment: Excessive thyroid hormone replacement can lead to iatrogenic hyperthyroidism with risks of cardiac arrhythmias and bone mineral density loss 4

4. Missing adrenal insufficiency: Starting thyroid hormone replacement without addressing concurrent adrenal insufficiency can precipitate an adrenal crisis 4

5. Ignoring special populations: Elderly patients, pregnant women, and those with cardiac disease require special consideration for dosing and monitoring 3

Early recognition and appropriate treatment of hypothyroidism are essential for preventing complications and improving quality of life.