Brief Answer:
Can be due to heart, however general work up would help better :)

Detailed Answer:
Hello, I am Dr. Mody and I would be addressing your concern here.
Now as I understand you are a 46 yr female who presently are hypothyroidism post Graves, and no medication apart from thyroxine.
Now the breathlessness you describe which is more on exertion like climbing stairs, points towards more of heart, however this breathlessness should subside once you rest.
Would like to ask are you still having those swelling in the lower legs, and any chest discomfort ot pain associated with breathlessness.
Apart from that do you smoke and if yes how much, how is your family history for heart problem, and did you have any lung issues prior to this.
For the vertical lines,
The causes are in numerous. However if I short list for you
1) vitamin deficiency
2) pre diabetes, because you had graves which is an autoimmune disease, and similarly diabetes is due to similar mechanism and for one you should get evaluated.
3) can be due to thyroid as well.

Now for evaluation.
Get the diabetes checked fasting and post lunch sugars, hemoglobin, thyroid profile, do include free t3 t4, because over treatment can lead to the symptoms you describe and so we can titre down the drug dose (heart palipation, and throwing).

For heart best would be ekg and stress test, which can determine whether the symptoms you describe are due to heart or not.
Also get your blood pressure checked and lungs examined by a local doctor.

This should be the precise and almost complete evaluation which I can recommend.
Also some more information we can narrow down the differentials, also you may upload last investigation you ever did.

Hoping I could help.
Regards Dr Priyank Mody

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