Brief Answer:
Thyroid

Detailed Answer:
Management of thyroid nodules and cancer, and post surgery for these conditions can be complex. Endocrinologists are best qualified and trained to handle this.
I see there is a long wait to see one though.

You seem to be suggesting your thyroid lobe was removed 10 years ago, because there was cancer. Would you recall which type of cancer it was.......Papillary, Follicular or another type? Also what was the size of the cancerous nodule in that lobe?

Generally, when Papillary/Follicular thyroid cancers are subjected to lobectomy, they are less than 1 cm in size with no local spread to lymph nodes. In such instances, suppression of TSH with higher than usual doses of Levo thyroxine (of which Synthroid is one brand name) are given for a few years after which the patient is presumed cured, provided periodic ultrasound examinations show no nodule(s) in the remainder of the thyroid.

It seems here levo thyroxine was not offered to you. Perhaps you did not have thyroid cancer then in the first place?
In any event, management approaches are individualized in many cases and only an endocrinologist who has the opportunity to see you in person and follow you over several years can make the best treatment plan for you.

Regarding the current situation of a high normal TSH with normal thyroid hormone levels, this is what I would do if I saw someone in my practice with your profile:
I would recommend blood tests for thyroid auto antibodies: anti TPO and anti Thyroglobulin.
If even one of these is positive you likely have 'Primary Acquired Mild/Subclinical Seropositive Permanent Hypothyroidism due to Chronic Hashimoto's Thyroiditis'. This long term simply means you have a mildly under active thyroid that may not necessitate treatment right away but authorities in the field have described several specific circumstances where treatment with levo thyroxine (25 to 75 mcg) can be offered if one or more of the following conditions are present:

1 (I will skip the conditions applicable to women, because you are male)

2 Neck swelling ('Goiter')

3 Positive thyroid auto antibodies

4 Compelling symptoms of hypothyroidism (which you say you dont have)

5 Heart failure

6 Atherosclerotic Cardiovascular disease (ie blockages in arteries of the heart/brain or legs from plaque build up), or risk factors for this to develop

Latest guidelines suggest treatment with levothyroxine should be considered for these select situations.

Further if thyroid antibodies are negative, I typically advise my patients to recheck in 2 months to see if the condition normalizes of its own accord because there is a condition called transient (temporary) thyroiditis that results in spontaneous recovery, and does not require any treatment.

In individuals older than 50, especially with heart disease it is advisable to start with low doses such as 12.5 to 25 mcg of levo thyroxine

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Brief Answer:
Follow up

Detailed Answer:
I see.

Thyroglobulin levels have no value in monitoring your thyroid cancer if you have one lobe intact and intentionally left behind.

What you have opted to do is something the latest guidelines are tending towards. New thyroid cancer management guidelines from the ATA (American Thyroid Association) are expected before the end of the year. I have preliminarily reviewed the recommendations and they seem to echo your approach.

I must say I am impressed that as a non-expert you made these tough decisions.

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