Clinical Signs of Hypothyroidism
Hypothyroidism presents with a constellation of symptoms reflecting decreased metabolic rate and tissue accumulation of polysaccharides, ranging from subtle nonspecific complaints to life-threatening manifestations. 1, 2
Cardinal Symptoms Due to Metabolic Slowing
Fatigue and lethargy are the most common presenting symptoms, affecting 68-83% of patients with hypothyroidism. 1, 3 This profound tiredness results from decreased metabolic rate and reduced thyroid hormone activity across multiple body systems 1.
- Cold intolerance occurs due to decreased heat production by the body 4, 2, 5
- Weight gain (affecting 24-59% of patients) results from decreased fat-burning rate despite no change in dietary habits 4, 2, 3
- Constipation develops from slowed gastrointestinal motility 1, 4, 2, 6
Cognitive and Neuropsychiatric Manifestations
- Intellectual slowness and cognitive impairment (affecting 45-48% of patients), including memory loss and difficulty concentrating 1, 3
- Depression is a common presenting symptom 1
- Somnolence (excessive sleepiness) 1
Dermatologic and Physical Examination Findings
Dry, coarse skin (xeroderma) is a hallmark finding on physical examination. 4, 2, 5 Additional cutaneous manifestations include:
- Periorbital puffiness from polysaccharide accumulation in tissues 7, 1
- Hair loss 1
- Cold skin to touch 7
- Myxedema (non-pitting edema/swelling) from mucopolysaccharide deposition 1
Cardiovascular Signs
Bradycardia (slow heart rate) is a characteristic cardiovascular finding. 1 Other cardiac manifestations include:
- Mild diastolic hypertension with narrowed pulse pressure 7, 1
- Pericardial effusions in severe cases 1
- Heart failure can develop if untreated 1, 4
Neuromuscular Findings
- Delayed ankle reflex is a specific physical examination finding 7, 1
- Muscle cramps and weakness, particularly proximal muscle weakness 1
- Slow movement 7, 1
Voice and Throat Changes
Reproductive and Metabolic Effects
- Menstrual irregularities (affecting approximately 23% of women), including oligomenorrhea and menorrhagia 3
- Infertility and increased miscarriage risk 3
- Insulin resistance and hyperglycemia in patients with diabetes 3
Laboratory Confirmation
Diagnosis requires biochemical confirmation with elevated TSH and low free T4 levels. 7, 1, 3 A TSH concentration less than 4-5 mIU/L effectively rules out peripheral hypothyroidism 6.
Critical Pitfall to Avoid
The signs and symptoms of hypothyroidism are nonspecific and nondiagnostic, especially early in disease presentation, making clinical diagnosis unreliable without laboratory confirmation. 5 Between 30-60% of elevated TSH levels normalize on repeat testing, emphasizing the need for confirmatory testing before initiating lifelong treatment 8, 6.
Life-Threatening Presentation
Untreated hypothyroidism may progress to myxedema coma, characterized by hypothermia, hypotension, and altered mental status, with mortality rates up to 30%. 3 This represents a medical emergency requiring intensive care unit management 3.