My doctor has warned me that I will develop hypothyroidism in the future based on a history of irregular blood tests (though i couldn't tell you any more detail), and have to have my levels tested every 6 months.
Should I feel developing hypothyroidism is inevitable, or can anyone suggest any possible modifications to diet/lifestyle/supplementation that could prevent it?
I am otherwise a healthy and fit female lacto-paleo 19yo, doing weights 4xweek and intervals 2x.
Would appreciate any advice anyone can offer, I just don't feel comfortable with the notion that my doctor has condemned me to this.
I would say no, don't feel that it's inevitable. But also, don't ignore it until it happens. Start your investigation now, because if it is not inevitable now, it may well become inevitable if you do nothing. And of course, depending on the cause, it may well be inevitable or even underway already. There are enough possible variations to this, that you just have to learn more.
As much of an un-fun project as this is going to be, you should consider educating yourself about the thyroid in general, and hypothyroidism in particular. It has various causes, and thus, various appropriate treatments.
Your doctor says "irregular bloodtests" so if it were me, I'd want copies of all those labs. But just getting the labs won't suffice if you don't know what they tested, or how to read the results. Most doctors do not order all the necessary tests, and most doctors will accept your results as fine so long as they fall within a standard range. But people aren't standardized, and your thyroid treatment (if you even need any) should be specifically designed for you, and should adequately address any quality of life issues and symptoms you have. Any treatment that makes lab tests look normal but leaves you feeling bad is not working.
I've lived with thyroid disease all my life, and unfortunately, in my ignorance I spent my 20's deteriorating under conventional, standardized treatment protocols. If one day your doctor announces that your labs finally show you are hypothyroid, and then takes out a prescription pad and prescribes Synthroid, levothyroxine, levoxyl, or really anything else, without having a complete discussion with you about the drugs, their pros and cons, and their alternatives, you might need a new doctor.
Thyroid hormone replacement therapy may indeed be in your future, maybe not. Maybe your thyroid test results come from other factors (iodine/selenium issues, autoimmune responses that can be diminished by dietary changes--I've read of connections to gluten-intolerance, for instance). Either way, thyroid problems left unaddressed practically ensure diminishing quality of life and health over time. But this can be avoided, and you can live almost unaware you even have the condition if you know what you're doing.
Here are resources I turn to for more thyroid information, and I know others will provide their own preferred resources too, so you'll have plenty of reading to get started on:
Chris Kresser's Thyroid Disorders Page -- Kresser provides a measured, thoughtful but thorough selection of articles exploring various aspects, causes, treatments for thyroid problems. Thyroid advocacy can get a little crazy or agenda-driven, so I like Kresser's equanimity.
Stop the Thyroid Madness -- What I said about Kresser and his equanimity above? Not so much here. This is a group of advocates with an agenda. But don't be too ready to easily dismiss them. They offer a ton of great information, as long as you bring your own functioning brain to the table and read critically. In the interest of disclosure, I followed their protocol to get off synthetic thyroid hormones and onto Armour Thyroid, and it was literally a life changing experience. Sometimes their tone turns me off, but they've helped me a lot, and in a funny way, led me to paleo by challenging my acceptance of conventional clinical medical practice, and demonstrating the frequent folly of government standards and recommendations.
Good luck! It's great that people come here because they're open to the idea that they can influence their own health outcomes. You're miles ahead of most people who are told they have thyroid (or any other) trouble by a doctor. And you seem young and healthy--right now--so you have the chance to intervene before you're not young and healthy anymore!
I can't help you much because I haven't gone through a thyroid issue myself, but I would suggest you ask the doc to give you more specific info (in a language you understand...not crazy doctor language). Perhaps you have an issue that can not be controlled with diet. You also have every right to have a copy of your blood tests so you can do your own research or consult with other medical professionals.
When I was your age, I was diagnosed with ideopathic pancreatitis (pancreatitis that occurred for no known reason) and hyperinsulinemia (blood insulin levels something like 5x's normal) - after years of poking and proding and painful episodes of pancreatitis, I was left with little info from the doc other than don't drink, eat a low-fat diet and take metamucil. Not much explanation other than that. I spent years trying to understand the problem, including how to control the problem, fearful that my pancreas would quit on me and leave me diabetic or dead. What I've learned is that I can control the issue with a lower carb, higher protein diet (fat really doesn't bother me either). I wish I had understood better what pancreatitis was when I was your age, because I do feel like perhaps I've lost some of my life living so many years with these problems (if nothing else, the enjoyment of eating, sleeping and doing anything active for fear that I might go hypoglycemic or have a pancreatitis attack).
An excess consumption of sugar and junk food in the diet should be avoided as it leads to depletion of vital nutrients from the body.
Avoid excess of alcohol, caffeine (as in fizzy drinks) and smoking as it decreases the immunity and nutrient level of the body which may lead to hampering of the thyroid function.
The fat content of the diet must go down and some amount of coconut oil is beneficial to the hypothyroid.
Other toxins like too many prescriptions and over the counter medications should not be irresponsibly consumed.
Often consumption of raw foods diet like sprouts, salads, vegetable juices, fruits also go a long way in helping the body to heal and recover.
Fish, kelp, seaweed, raw nuts are beneficial is Hypothyroidism.
Goitrogens like cabbage, broccoli, cauliflower, soya should be consumed in very small amounts only.
Foods used in the treatment of low levels of thyroid, besides seafood and sea vegetables should be rich in vitamin A, vitamin E, B complex, vitamin C, zinc, iodine etc.
Besides foods, regular walk is a must to lift the mood and decrease water retention.
Don't buy into it! Doctors are trained to be afraid of the body and push it into submission. Kundalini yoga is the yoga of glandular health - Ravi Singh and Anna Brett's yoga DVD's coupled with Pure Essential Oils have done wonders for my thyroid and other glands.