Could be several thyroid issues. Low TSH with low normal FTs could indicate hypothyroidism, Adrenal Fatigue or other problems such as allergies, hormonal imbalance, yeast.
Graves' disease the FT-3 would be really high.
Hyperthyroidism FTs would be high.
Unless you have a nodule, a biopsy is not necessary. Your levels on how they relate to each other will and can tell your thyroid condition, and an uptake will and can verify.
Good Luck.
Well, I know that lupus is an autoimmune disorder. I also know that when you have one autoimmune disorder, you very often have another. Grave's disease is an autoimmune disorder of the thyroid that causes your TSH to be incredibly low (hyperthyroidism). I would recommend and u/s and biopsy of the thyroid to see if that's what it is.