Hypothyroidism Assessment

Primary, Subclinical & Central Hypothyroidism

View Algorithm

Key Clinical Points

• TSH is the single best screening test for primary hypothyroidism
• Confirm with FT4 when TSH is elevated
• Subclinical: treat if TSH >10, or TSH 4-10 with symptoms/TPO+/pregnancy
• Central hypothyroidism: low FT4 with low/normal TSH — do NOT rely on TSH alone
• Always rule out adrenal insufficiency before starting levothyroxine

Demographics

Patient age

Age affects presentation and management approach

Biological sex

Thyroid disease 4-8x more common in females

Is the patient pregnant or planning pregnancy?

Pregnancy significantly alters management approach

Symptoms

Fatigue or lethargy

Present in >90% of hypothyroid patients

Unexplained weight gain

Common in hypothyroidism due to decreased metabolism

Cold intolerance

Due to decreased thermogenesis

Constipation

GI motility decreased in hypothyroidism

Dry skin or hair changes

Myxedematous changes

Menstrual irregularities (menorrhagia)

Menorrhagia common in hypothyroidism

Cognitive slowing or memory impairment

Central nervous system effects

Depression or low mood

Associated with hypothyroidism

Muscle cramps or stiffness

Myopathy in hypothyroidism

Hoarse voice

Myxedematous infiltration of vocal cords

Risk Factors

Family history of thyroid disease

Increased risk of autoimmune thyroid disease

Personal history of autoimmune disease

Associated with autoimmune thyroid disease

Iodine intake status

Affects etiology and management

Medications

Current medications affecting thyroid

Amiodarone

Lithium

Levothyroxine

Carbimazole/Methimazole

Biotin supplements

Tyrosine kinase inhibitors

Immune checkpoint inhibitors

Iodine-containing contrast

None

Multiple drugs affect thyroid function

Recent iodine-containing contrast (within 3 months)

Can cause thyrotoxicosis or interfere with RAI uptake