Cortisone as an oral drug is another common issue (e.g. prednisolone). Cortisone may cause weight gain in the long run, especially at higher doses (e.g. more than 5 mg prednisolone per day). Unfortunately, cortisone is often an essential medication for those who are prescribed it, but the dose should be adjusted frequently so you don’t take more than you need. Asthma inhalers and other local cortisone treatments, like creams or nose sprays, hardly affect weight.
Your doctor can easily arrange for you to take a blood test to measure the concentration of thyroid stimulating hormone (TSH). If the test comes back and everything looks good, your thyroid gland is probably fine. For a more exact diagnosis, you can ask them to measure the actual levels of thyroid hormones in the blood (T3 and T4), as sometimes these are low even if the TSH is within the fairly broad normal range.
For even more impressive effects on body composition, aim for exercise forms which elicit a positive hormonal response. This means lifting really heavy things (strength training), or interval training. Such exercise increases levels of the sex hormone testosterone (primarily in men) as well as growth hormone. Not only do greater levels of these hormones increase your muscle mass, but they also decrease your visceral fat (belly fat) in the long term.