The above described findings are impressive of chronic lymphocytic (Hashimoto's) thyroiditis (in the clinical setting of hypothyroidism).
Hashimoto's thyroiditis is chronic lymphocytic / autoimmune thyroiditis. The patients shows mild transient hyperthroisim, followed by euthyroidism & finally fibrosis ensues and the patient is hypothyroid (thyroid replacement therapy is indicated). Ultrasound shows enlarged lobulated heterogenous gland with a myriad of tiny hypoechoic nodules, fibrosis occurs in the late stages with dense echogenic fibrous septa. Thyroid scintigraphy shows decreased uptake. Hashimoto's thyroidits can be complicated by thyroid lymphoma.
The differential diagnosis is:
Primary thyrotoxicosis (Grave's disease): the gland is diffusely and homogenously enlarged. The patient is hyperthroid. Thyroid scintigraphy shows diffuse homogenously increased uptake. Early Hashimoto's thyroiditis may mimic 1ry thyrotoxicosis ( the gland is enlarged with increased vascularity and increased uptake at scintigraphy); however the patient is usually euthyroid in early Hashimoto's thyroiditis.
Secondary thyrotoxicosis (Plummer's disease): Enlarged heterogenous gland with patchy areas of increased vascularity. Toxic nodules show incresed vascularity and increased uptake at thyroid scintigraphy with inhibition of the uptake of the rest of the gland.
- Subacute granulomatous "De-Quervain-thyroiditis": PAINFUL thyroiditis; usally post-viral. The patient is intially presenting with hyperthroidism due to release of the thyroid hormones into the circulation by the destructed thyroid follicles, followed after 2-4 months by hypothroidism due to depleted follicles. Finally, after 2 months, the patient return to the euthyroid state. The gland appears mildly enlarged and slightly hypoechoic with increased vascularity. Thyroid scintigraphy shows decreased uptake.
Subacute lymphocytic thyroiditis: PAINLESS thyroiditis; usually in young women and may be post-partum. Minimally enlarged gland with hyperthyroidism that returns to normal euthroid state.
Riedel thyroidtis is a differential of fibrosing Hashimoto's thyroiditis.