Could this be hypothyroidism?

Could This Be Hypothyroidism?

Yes, hypothyroidism is a common endocrine disorder that should be considered when patients present with nonspecific symptoms like fatigue, weight gain, cold intolerance, constipation, cognitive issues, or menstrual irregularities. 1, 2

Key Clinical Presentations to Recognize

Hypothyroidism manifests with symptoms due to metabolic slowing that can be subtle and overlap with other conditions:

• Fatigue occurs in 68-83% of patients with hypothyroidism 1
• Weight gain affects 24-59% of patients 1
• Cognitive impairment (memory loss, difficulty concentrating) presents in 45-48% of cases 1
• Menstrual irregularities (oligomenorrhea, menorrhagia) occur in approximately 23% of women 1
• Cold intolerance, constipation, and dry skin are classic manifestations resulting from decreased metabolic rate 2, 3

Diagnostic Approach

Measure serum TSH as the primary screening test, with sensitivity above 98% and specificity greater than 92%. 4 If TSH is elevated, measure free T4 to distinguish between subclinical and overt hypothyroidism 5, 6:

• Overt primary hypothyroidism: Elevated TSH with low free T4 1, 7
• Subclinical hypothyroidism: Elevated TSH (typically >4.5 mIU/L) with normal free T4 4, 5
• Central hypothyroidism: Low or inappropriately normal TSH with low free T4 8, 6

Critical Pitfall to Avoid

Do not diagnose based on a single elevated TSH value—30-60% of elevated TSH levels normalize spontaneously on repeat testing. 5 Confirm with repeat TSH and free T4 measurement after 3-6 weeks 5.

Who Should Be Tested

While routine screening of asymptomatic adults is not recommended 4, 1, targeted testing is appropriate for:

• Patients with type 1 diabetes (17-30% develop autoimmune thyroid disease) 4, 1
• Pregnant women or those planning pregnancy 5, 7
• Patients with symptoms suggestive of thyroid dysfunction 4, 3
• Elderly patients, particularly women (prevalence increases with age) 1, 3
• Patients with history of neck radiation or thyroid surgery 1, 2
• Patients on certain medications (immune checkpoint inhibitors, amiodarone) 1, 2

Treatment Thresholds

Initiate levothyroxine therapy for all patients with overt hypothyroidism (elevated TSH with low free T4). 7, 3

For subclinical hypothyroidism, treatment decisions depend on TSH level:

• TSH >10 mIU/L: Treat regardless of symptoms, as this carries approximately 5% annual risk of progression to overt hypothyroidism 5, 7
• TSH 4.5-10 mIU/L: Consider treatment for symptomatic patients, pregnant women, those with positive anti-TPO antibodies, or patients with infertility 5, 7

Consequences of Untreated Hypothyroidism

Untreated hypothyroidism can lead to serious complications affecting multiple organ systems:

• Cardiovascular: Heart failure, increased risk of cardiovascular events, hypertension, dyslipidemia 1, 3, 9
• Metabolic: Insulin resistance, hyperglycemia in diabetic patients 1
• Reproductive: Disrupted ovulation, infertility, increased miscarriage risk 1, 2
• Severe decompensation: Myxedema coma with hypothermia, hypotension, altered mental status (mortality up to 30%) 1, 2

Common Etiologies

Hashimoto thyroiditis (autoimmune disease) causes up to 85% of primary hypothyroidism in areas with adequate iodine intake. 1 Other causes include radioiodine treatment, thyroidectomy, iodine deficiency, and certain medications 1, 2, 9.

Special Populations Requiring Heightened Suspicion

• Children with type 1 diabetes: Measure TSH at diagnosis when clinically stable, then recheck every 1-2 years 4
• Postpartum women: Higher risk for autoimmune thyroid disease 4
• Patients with Down syndrome: Symptoms may overlap with baseline condition 4
• Elderly patients: Symptoms may be particularly subtle 4, 3