Endocrine · Year 2 · from Endocrine

Case 2: Hashimoto's Thyroiditis with Hypothyroidism

Patient Demographics

  • Age: 42 years
  • Sex: Female
  • Occupation: Librarian

Chief Complaint

"I'm exhausted all the time, I've gained weight, and I'm always cold."

History of Present Illness

A 42-year-old woman presents with a 6-month history of progressive fatigue, weight gain (12 pounds), cold intolerance, and constipation. She reports feeling "slowed down" mentally, with difficulty concentrating and memory problems. Her voice has become hoarse, and her skin and hair have become dry. She has noticed swelling in her face and hands. Her menstrual periods have become heavier and more frequent. She has a sister with type 1 diabetes.

Physical Examination

  • Vital Signs: BP 142/92 mmHg, HR 56 bpm, Temp 36.2°C
  • General: Overweight, fatigued-appearing woman with slow movements and speech
  • Face: Periorbital puffiness, dry, coarse features
  • Neck:
  • Thyroid gland firm, rubbery, diffusely enlarged (1.5x normal)
  • Non-tender, irregular/pebbly texture
  • No nodules, no bruit
  • Cardiovascular: Bradycardia, distant heart sounds
  • Skin: Dry, cool, rough texture; non-pitting edema of hands and face (myxedema)
  • Hair: Coarse, brittle; lateral eyebrow thinning
  • Reflexes: Delayed relaxation phase ("hung-up" reflexes)

Workup

  • Laboratory Studies:
  • TSH: 68 mIU/L (markedly elevated)
  • Free T4: 0.4 ng/dL (low)
  • Anti-TPO antibodies: >1000 IU/mL (markedly elevated)
  • Anti-thyroglobulin antibodies: 245 IU/mL (elevated)
  • Lipid panel: Total cholesterol 268 mg/dL, LDL 178 mg/dL (elevated)
  • CBC: Hemoglobin 10.8 g/dL (mild anemia)
  • Ultrasound Thyroid: Diffusely heterogeneous, hypoechoic gland with increased vascularity; no discrete nodules

Diagnosis

Hashimoto's thyroiditis (chronic lymphocytic thyroiditis) with overt primary hypothyroidism

Treatment

  1. Levothyroxine replacement:
  • Starting dose: 1.6 mcg/kg/day (full replacement) in otherwise healthy patients
  • In elderly or cardiac patients: Start low (25-50 mcg) and titrate slowly
  • Take on empty stomach, 30-60 minutes before breakfast or at bedtime
  1. Monitoring:
  • Recheck TSH in 6-8 weeks
  • Titrate levothyroxine by 12.5-25 mcg increments
  • Goal: TSH in normal range (usually 0.5-2.5 mIU/L)
  1. Long-term:
  • Annual TSH monitoring once stable
  • Watch for drug interactions (calcium, iron, PPI)
  • Screen for other autoimmune conditions (celiac, adrenal insufficiency)

Clinical Pearl

Hashimoto's thyroiditis is the most common cause of hypothyroidism in iodine-sufficient regions and is characterized by lymphocytic infiltration of the thyroid with positive anti-TPO and/or anti-thyroglobulin antibodies. It is associated with other autoimmune conditions (type 1 diabetes, celiac disease, vitiligo, Addison's disease). The delayed relaxation phase of reflexes (pseudo-myotonic reflex) is a classic finding of hypothyroidism. Levothyroxine absorption is affected by many factors - patients should be counseled about consistent timing, avoiding calcium/iron supplements within 4 hours, and informing their doctor of any new medications.

Clinical Image

Thyroid ultrasound showing diffusely heterogeneous, hypoechoic parenchyma with fibrous bands characteristic of Hashimoto's thyroiditis.

Image Source: Radiopaedia - "Hashimoto thyroiditis" License: CC BY-NC-SA 3.0 URL: https://radiopaedia.org/cases/hashimoto-thyroiditis-3

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