Help me understand, please?

I just joined Healing Well, found this area and hope that all of your combined experience/knowledge will help me understand what's going on with my thyroid. I've been on synthroid for close to 40 years. Diagnosed hypothyroid in my 20's; began 25 mcg at that time. TSH was checked regularly and over time, the dosage increased as needed to the point that, 2 years ago, I was taking 200 mcg. Then I started having significant swings in my TSH levels and my doc started trying to adjust the meds by lowering the synthroid 25 mcg/every 6 weeks. This continued until December, 2015 when my TSH dropped to <0.01 u[iU]ML, range (0.3-5.5). By then I was at 150 mcg. TSH tested at the same level in Feb., 2016 and the synthroid was lowered again to 125 mcg. Then, in July, 2016, TSH jumped to 10.33 and the synthroid was lowered to 112 mcg. On 9-1-2016, TSH was at 6.76 and Free T4 at 1.1 (ng/dl (0.9-1.8). Synthroid decreased to 100 mcg. On 10-18-2016, TSH was at 11.29. Synthroid increased to 125 mcg. I have never had swings like this before. Thoughts?

Thanks, hypoHashimoto. Cause unknown and I do have Hashimoto. I see an endo regularly and 2 recently.

I just re-read my question and saw that I've left a few things out. During 9 months of the timeframe I described, I was kept at 125 mcg and STILL had the crazy TSH swings.

I recently had a CT done and 2 nodules (not goiter) were seen on my thyroid. They are on the top and bottom parathyroids on the right side of my thyroid. I think that could be the cause but 2 different endos don't think so.

One is on the thyroid itself and the other on the lower parathyroid on the right side.