Christina is a 22-year-old female with no significant past medical history. She is presented with weight loss despite good appetite. She also complains of heat intolerance, profuse sweating, and palpitations. She said that these symptoms had started about 3-month ago. She recently went to a walk-in clinic with a slight increase in her body temperature and was given symptomatic treatment for common cold, but she did not feel better. Her symptoms became even worse.

On examination:

• Height: 165 cm, Weight: 62.7 kg (was 67 kg 3 months ago), BMI: 23
• BP: 145/60 mmHg, Heart rate: 112/min, Respiratory rate: 20/min, Temperature: 37.3 ⁰C, O2SAT: 98%
• Staring look, lid lag, proptosis. Sweaty hands with thin skin. Fine tremor. Diffusely enlarged, non-tender mass on the anterior neck

According to the patient’s symptoms and signs, which organ is affected and requires further assessment?

Christina's laboratory tests showed:

• Blood analysis:
  • CBC:
    • Hemoglobin: 120 g/L, Hematocrit: 0.35,
    • RBCs: 3.6 x 10¹²/L, MCV: 93 fL, MCH: 26 pg, RDW: 14.2%, Reticulocytes: 0.9%, ESR: 18 mm/hour
    • WBC: 4.9 x 10⁹/L, (Neutrophils: 2.9 x 10⁹/L, Lymphocytes: 2.0 x 10⁹/L, Basophils: 0.02 x 10⁹/L, Eosinophils: 0.18 x 10⁹/L, Monocytes: 0.0.6 x 10⁹/L)
    • Platelet counts: 287 x 10⁹/L
  • Na: 142.2 mmol/L, K: 4.3 mmol/L, Glucose: 5.2 mmol/L, Creatinine: 80.2 umol/L, Uric acid: 210 mmol/L
  • Triglycerides: 1.9 mmol/L, Cholesterol: 3.5 mmol/L, HDL: 1.3 mmol/L, LDL: 1.9 mmol/L
  • Bilirubin: 10 mmol/L, Albumin: 43.8 g / L, AST: 22 U/L, ALT: 34 U/L
  • TSH: 0.02 uU/mL, Total T₄: 363 nmol/L, Free T₄: 36 pmol/L, Total T₃: 11 nmol/L, Free T₃: 14 pmol/L,
  • Anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibody tests: positive

• Urinalysis: Color: light yellow, pH: 6.4, Specific gravity: 1020, Osmolarity : 597 mmol/kg; Glucose, Ketones, Albumin, Bilirubin: negative, WBCs and RBCs: 1 and 2/HPF, Epithelial cells, Casts, Bacteria, Yeast: negative.

Select all the tests that show abnormal values! (select all that apply)  Before you go to the next question, think about an explanation of these abnormal laboratory values.

You can also notice that Christina has anti-thyroid peroxidase (anti-TPO) antibody in her blood. What is the role of the thyroid peroxidase?

What is the clue in the final diagnosis of Christina’ s condition? (Pick only one)