I have met others that did not
gain weight at all - just had the high cholesterol etc.
Weight gain is a symptom but NOT every symptom happens to everyone. I did not gain for 6 years (of the dang 12 it took to get diagnosed) and then when I did - it was fast and furious...
You probably have symptoms - but they are very subtle - low libido, depression, no /impaired sleeping, acne, fatigue, poor healing, hair changes, etc. All symptoms of something else but they oddly will not respond to meds...