Can thyroid hormone medicine make your hair weak?

Maybe ;) The thyroid hormone medicine should not affect your hair directly. However, if your dosage is low, it can indeed affect your hair, as well as cause many other symptoms. If you are having such a problem, some lab tests with your primary doctor should help identify the problem. If you are taking thyroid hormone, you should have your levels checked at least yearly.
Not usually. Typically the condition of low thyroid hormone is associated with weak hair. The medicine should help to reverse it.
Thyroid dysfunction. Weak and brittle hair is one of the hallmark signs of thyroid dysfunction. Accurate evaluation of the current thyroid regimen is necessary if a patient is experiencing more symptoms.

Related Questions

Can low thyroid hormone symptoms like hair-loss be reversed?

Yes. But it takes time to recover losses from hypothyroidism. It's most serious consequence is in the newborn when undetected causing a cretin, a form of idiocy due to absence of thyroid during the neonatal and infancy period. My all a's athletic daughter could have been one, but all neonates were screened whee she was born.
Allopecia. If scalp hair loss called allopecia is due to hypothyroidism one can reverse it by normalizing thyroid function. Most of the time hypothyroidism is due to an autoimmune disorder called hashimotos disease. Allopcia is an accompanying autoimmune disorder and may not be due to low thyroid hormones. It's an association -- not causation.
Yes. Usually when thyroid hormone levels are stablized the hair loss tends to be reversed. This may take weeks to months.

Can low thyroid hormone symptoms such as hair loss be reversed?

Possibly/depends,,,, This may be reversed depending on how severe and long-standing the thyroid issue is and how good a person's circulation is. Strict adherence to therapy would also help.

What kinds of tests are a ferritin level, thyroid hormone, free testosterone level? Tests for hair thinning or hair loss.

Overall health. Every man should have an occasional serum ferritin since hemochrmoatosis is common, deadly and treatable. Testosterone assays are of little value in a baldness workup despite what you may hear, but worthwhile in an erectile dysfunction workup. Hypothyroidism leads to a non-male-pattern baldness and thyroid screen is worthwhile every few years.