Your reports suggest autoimmune hypothyroidism likely Hashimoto’s.
TSH is high 17.8 with low normal T3,T4, and anti TPO & anti thyroglobulin antibodies are elevated.
Start
thyroid hormone replacement as per weight and repeat TSH in 8 weeks for dose adjustment.
This condition is common and well controlled with medication.
Avoid self dosing proper titration is important.
Feel free to consult, I can guide you with exact dosing and follow up plan.