What are the typical signs and symptoms of hypothyroidism?

Hypothyroidism Symptoms

Hypothyroidism presents with a constellation of symptoms reflecting metabolic slowing across multiple organ systems, ranging from subtle nonspecific complaints to life-threatening manifestations if left untreated.

Classic Metabolic and Constitutional Symptoms

The hallmark symptoms of hypothyroidism stem from decreased metabolic rate and reduced thyroid hormone activity throughout the body:

• Fatigue and lethargy are the most common presenting symptoms, reported by 68-83% of patients with hypothyroidism, reflecting the profound impact of thyroid hormone deficiency on cellular energy metabolism 1, 2
• Weight gain and difficulty losing weight occur in 24-59% of patients due to decreased basal metabolic rate and reduced fat oxidation 1, 2
• Cold intolerance develops as thyroid hormone deficiency reduces thermogenesis and heat production by the body 3, 4, 5
• Constipation results from slowed gastrointestinal motility affecting the entire digestive tract 2, 3, 4

Cognitive and Neuropsychiatric Manifestations

Thyroid hormone is critical for normal brain function, and deficiency produces characteristic mental status changes:

• Cognitive impairment including memory loss, difficulty concentrating, and intellectual slowness affects 45-48% of patients 1, 2
• Depression is a frequent manifestation of hypothyroidism and may be the primary presenting complaint 2, 3
• Somnolence (excessive sleepiness) reflects the overall metabolic slowing 2
• In severe untreated cases, altered mental status can progress to myxedema coma, a life-threatening emergency with up to 30% mortality 1

Dermatologic and Hair Changes

Thyroid hormone deficiency produces characteristic skin and hair alterations:

• Dry skin (xeroderma) is one of the most common symptoms, resulting from decreased sweat gland activity 3, 4, 5
• Coarse skin texture with decreased elasticity 2
• Hair loss affecting scalp hair, with coarse, brittle hair quality 2, 5

Cardiovascular Manifestations

Hypothyroidism causes specific hemodynamic changes that produce cardiovascular symptoms:

• Bradycardia (slow heart rate) develops as thyroid hormone normally increases heart rate and contractility 2
• Mild diastolic hypertension with narrowed pulse pressure occurs due to increased systemic vascular resistance (up to 50% elevation) 2
• Pericardial effusions can develop in severe cases 2
• Heart failure may result from decreased cardiac contractility, delayed ventricular relaxation, and abnormal cardiac output 2, 1
• Untreated hypothyroidism increases risk for cardiovascular events and can worsen pre-existing heart disease 1

Musculoskeletal Symptoms

Thyroid hormone deficiency affects muscle function and reflexes:

• Muscle weakness, particularly proximal muscle groups 2
• Muscle cramps are common 2
• Delayed ankle reflex is a characteristic physical examination finding 2
• Slow movement reflecting overall metabolic slowing 2

Fluid Retention and Edema

Hypothyroidism causes characteristic patterns of fluid accumulation:

• Periorbital puffiness is often an early manifestation 2
• Myxedema (non-pitting edema/swelling) results from accumulation of glycosaminoglycans in tissues 2
• Peripheral edema develops due to increased transcapillary escape of albumin and fluid retention 2

Voice and Throat Changes

• Hoarseness and voice changes occur due to myxedematous infiltration of the vocal cords 2, 3

Reproductive and Metabolic Effects

• Menstrual irregularities including oligomenorrhea and menorrhagia affect approximately 23% of women with hypothyroidism 1
• Infertility and disrupted ovulation can result from thyroid hormone deficiency 1
• Increased risk of miscarriage in pregnant women with untreated hypothyroidism 1
• Insulin resistance and hyperglycemia can develop or worsen in patients with diabetes 1

Laboratory Findings

The biochemical diagnosis is established by:

• Elevated thyroid-stimulating hormone (TSH) with sensitivity >98% and specificity >92% for detecting thyroid dysfunction 6, 2
• Low free thyroxine (T4) in overt hypothyroidism 6, 2
• Normal free T4 with elevated TSH defines subclinical hypothyroidism 6

Life-Threatening Presentation: Myxedema Coma

Severe untreated hypothyroidism can progress to myxedema coma, a medical emergency requiring intensive care unit management:

• Hypothermia (core temperature often <95°F) 1
• Hypotension and cardiovascular collapse 1
• Altered mental status ranging from confusion to coma 1
• Mortality rate up to 30% even with treatment 1

Important Clinical Caveats

The signs and symptoms of hypothyroidism are nonspecific and nondiagnostic, especially early in disease presentation 4. Symptoms can overlap with many other conditions and may go unnoticed or be attributed to aging, stress, or other factors 5. Clinical presentation differs with age and sex—older patients may present with predominantly cardiovascular or cognitive symptoms rather than classic metabolic complaints 3, 7.

Diagnosis cannot be made on clinical grounds alone and requires biochemical confirmation with thyroid function testing 4. The wide variety of clinical presentations ranges from completely asymptomatic (detected only on laboratory screening) to life-threatening myxedema coma 7.