What could raise TSH after years of stability?

I (56m) had my thyroid completely removed 30 years ago and for the past 10 years at least my medication has been stable at 100mcg Levothyroxine per day.

Last year my TSH had gone to 5.4 and the doctor wanted me to have another test but I stupidly forgot until recently, and now TSH is at 17.2

He has bumped me up to 150mcg per day.

Over recent couple of years I have been much more sensitive to cold, found it hard to drop weight, and am often tired.

Other medications I am on include a high blood pressure pressure and cholesterol rosuvastatin and ezetimibe combination. I take all the meds together each morning before eating.

Any ideas why it would change after years of stability?