What could be the cause of feeling extremely cold at night, particularly in older adults or individuals with a history of hypothyroidism, anemia, or diabetes?

Feeling Extremely Cold at Night: Key Differential Diagnoses

Feeling extremely cold at night is most commonly a symptom of hypothyroidism, but also warrants evaluation for anemia, diabetes-related complications, cardiovascular disease, and sleep disorders—particularly in older adults.

Primary Consideration: Hypothyroidism

Hypothyroidism should be the first condition considered when a patient reports cold intolerance, especially at night. 1, 2

• Cold intolerance is one of the classic presenting symptoms of hypothyroidism, occurring alongside fatigue (68-83%), weight gain (24-59%), and cognitive issues (45-48%) 2, 3
• The symptom results from decreased metabolic rate and reduced heat production by the body 4
• Hypothyroidism is more common in women and older adults, with prevalence ranging from 0.3% to 12% worldwide 2
• In women with obstructive sleep apnea, hypothyroidism is a particularly common association 1
• Dry skin (xeroderma) and constipation frequently accompany the cold intolerance 4, 3

Initial diagnostic approach: Measure thyroid-stimulating hormone (TSH) and free thyroxine (T4) levels; elevated TSH with low free T4 confirms overt primary hypothyroidism 2, 3

Secondary Consideration: Anemia

Anemia should be evaluated, particularly in patients with known hypothyroidism or unexplained fatigue. 5

• Anemia occurs in 20-60% of patients with hypothyroidism and may be the first presenting sign 5
• Microcytic anemia can result from iron malabsorption or menorrhagia 5
• Macrocytic anemia may indicate vitamin B12 or folate deficiency; pernicious anemia occurs 20 times more frequently in hypothyroid patients 5
• Normocytic anemia represents an adaptation to decreased basal metabolism from thyroid hormone deficiency itself 5

Diagnostic testing: Complete blood count, iron studies, vitamin B12, and folate levels should be obtained 5

Cardiovascular and Metabolic Causes

Diabetes Mellitus

• Diabetes is associated with temperature dysregulation and should be screened for in patients with excessive thirst or unexplained symptoms 1
• Hypothyroidism can cause insulin resistance and hyperglycemia in diabetic patients 2
• Baseline HbA1c testing is recommended in the initial evaluation 1

Cardiovascular Disease

• Congestive heart failure and hypertension are associated with nocturnal symptoms and should be evaluated 1
• Screen for ankle swelling, shortness of breath on exertion, and orthostatic symptoms 1
• Blood pressure assessment is part of baseline investigations 1

Sleep Disorders Contributing to Nocturnal Symptoms

Obstructive Sleep Apnea (OSA)

OSA should be strongly considered in older adults with nocturnal symptoms, particularly those with hypothyroidism, heart disease, or stroke history. 1

• OSA is associated with hypothyroidism, especially in women 1
• Cardinal symptoms include excessive daytime sleepiness, snoring, observed apnea, and nocturia 1
• Risk factors include age, obesity (neck collar size >17 inches in men, >16 inches in women), and anatomic upper airway abnormalities 1
• OSA contributes to cardiovascular disease, difficult-to-control hypertension, and cognitive impairment 1

Screening approach: Use the Epworth Sleepiness Scale and Berlin Questionnaire; confirm diagnosis with polysomnography 1

Other Sleep Disorders

• Insomnia, restless legs syndrome, and periodic limb movements should be screened for with targeted questions 1
• Ask: "Do you have problems sleeping aside from needing to get up to urinate?" and "Do you wake up without feeling refreshed?" 1

Medication-Induced Causes

Review all medications, as multiple drug classes can cause or exacerbate cold intolerance and sleep disturbances. 6, 7

• β-blockers (e.g., propranolol) contribute to cold extremities and sleep disruption 6
• Diuretics cause nocturia leading to sleep fragmentation 6
• Sedative-hypnotics and opiate analgesics should be reviewed 1

Recommended Diagnostic Algorithm

Step 1: Obtain thyroid function tests (TSH, free T4) as the highest-yield initial test 2, 3

Step 2: Perform complete blood count to evaluate for anemia 5

Step 3: Check electrolytes/renal function, calcium, and HbA1c 1

Step 4: Screen for sleep disorders using validated questionnaires if symptoms suggest OSA or other sleep pathology 1

Step 5: Assess blood pressure and evaluate for cardiovascular disease if indicated by history or examination 1

Critical Pitfalls to Avoid

• Do not dismiss cold intolerance as normal aging—it often indicates underlying hypothyroidism that requires treatment to prevent serious complications like heart failure and myxedema coma 2, 8
• Do not overlook OSA in patients with hypothyroidism—the conditions frequently coexist and both require treatment 1
• Do not attribute symptoms solely to one diagnosis—multiple conditions often coexist in older adults (e.g., hypothyroidism with anemia, OSA with cardiovascular disease) 1, 2
• Do not forget medication review—many commonly prescribed drugs contribute to temperature dysregulation and sleep disturbance 6, 7