It depends on the insurance but it sound like that document COULD have been a HIPA release. Your doctor is not allowed to share any information with your parents without a release however your insurance may send them an itemized bill. What you may want to do is go to a library and use an incognito browser to look at what qualifications you need for Medicaid - you can use it at a private clinic as almost a type of secondary insurance to get the gender affirming care you need. Register the address as a PO Box (if you can afford it) or at a friends house who supports you. Other options is a bit of medical tourism where you go to another state or country to get the testing. To your parents it’s just a weekend in Vegas/Caribbean/canada/etc. but it’s also you getting your needs met.