You are welcome!
Hashimoto's thyroiditis, the most common cause of hypothyroidism state, is an inflammation of the thyroid gland with autoimmune nature (your own immune system detects your thyroid gland as a foreign part and produces antibodies against thyroid gland).
Actually, these antibodies, known as anti-thyroid peroxidase antibodies, are directed towards thyroid peroxidase, an enzyme (protein) found within the thyroid gland.
Interaction between enzyme and antibodies leads to inflammation of the gland, eventually, resulting in destroyed gland and lack of thyroid hormones.
Patients with Hashimoto's, usually, experience swelling of the thyroid gland (due to the inflammation), leading to a feeling of tightness or fullness in the throat.
And, also, the enlarged thyroid gland is felt as a lump in the front of the neck, called a goiter.
Have a good, healthy day!
Marija