The main control of your temperature/metabolism is by your thyroid. Raynauds syndrome affects appendages; usually fingers, secondly toes, nose and ears. These areas Blanche and hurt when exposed to cold. This doesn't sound anything like your symptoms.

Anemia is a potential cause unlikely in a young male and can easily be ruled out with a CBC.

Checking TSH, T4 and T3 (total and free) would be a first step with knowing the thyroid is putting out enough hormone. The normal ranges for these hormones are ridiculously wide. But if your T3 is toward the top end of the range you at least know your thyroid is putting out enough juice. This still doesn't tell you how it is working at the receptors. People gradually become less sensitive to thyroid hormone as they age just like they become less sensitive to insulin. Although at 18 years of age this would be unlikely to have happened yet.

To tell if this is metabolism related, there is simple in office testing that can measure your resting metabolic rate. Part of my practice is weight loss, so I happen to have such equipment in my office.

If I were evaluating you I would do a complete history, physical and a battery of blood tests along with a resting metabolic rate. If I didn't find anything other than a low metabolism, and other signs or symptoms of hypothyroidism, regardless of ''normal'' thyroid labs I would empirically prescribe T3 and titrate it up to see if cold intolerance and other thyroid symptoms responded.

Fatigue is by far the most common symptom of hypothyroidism but cold intolerance, dry skin, weight gain, hair loss and poor motivation often go along with the fatigue. These symptoms become more and more common as people get older..... even though their thyroid tests remain "normal".

They go to the doctor asking to have their thyroid checked and are frustrated to be told her test normal and that the symptoms just go along with getting older. This is of course true. But what the doctors don't realize is that as people age, they become less sensitive to their thyroid hormone.

If you look at the symptoms of aging and of hypothyroidism you see there are a lot of similarities. That is because everyone becomes less sensitive to their thyroid hormone as they age.

I explained it to my patients this way..... When you're six years old jumping on the bed your thyroid hormone was high and you were sensitive to it. By the time you're 20 years old your thyroid hormone output has already dropped and you're starting to become less sensitive to it. Even though your thyroid hormones may remain "within normal limits" you are getting hypothyroid symptoms as you age because you're becoming less sensitive to the hormone.

So in those cases I do a complete history, physical and battery of tests including resting metabolic rate and consider titrating T3 up to treat those hypothyroid symptoms. Though in most cases I do have a trick that often works to re-sensitize them to their own thyroid hormone. In those cases they either do not need T3 or need less of it to control their symptoms.

I do not have many 18-year-olds coming in with hypothyroid symptoms but over the years have treated probably 10 or 20 teenagers for symptoms of hypothyroidism.

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For a teenager like you cold intolerance suggests inactivity. This is barring any established diagnosis of endocrine malfunction or insufficiency. The control of core body temperature by the brain hypothalamus is accomplished through hormonal control of body metabolism. An active life style keeps the thyroid gland, the adrenal gland, small blood vessels and the liver active and well developed in their metabolic functions. The artereoles and venues in particular coordinate with the peripheral nervous system to limit heat loss through sweat when the body metabolism is low. Your doctor may need to run complete metabolic and hormonal panels on you to see which regulatory components are deficient. In the mean time get involved in some cardio and aerobic workouts or sports.

For a teenager like you cold intolerance suggests inactivity. This is barring any established diagnosis of endocrine malfunction or insufficiency. The control of of core body temperature by the brain hypothalamus is accomplished through hormonal control of body metabolism. An active life style keeps the thyroid gland, the adrenal gland, the blood small blood vessels and liver active and we'll developed in their metabolic functions. The arterial es and venues in particular coordinate with the peripheral nervous system to limit heat loss through sweat when the body metabolism is low. Your doctor may need to run a complete metabolic and hormonal panels on you to see which regulatory components are deficient. In the mean time get involved in some cardio and aerobic workouts or sports.

Your internal thermostat is out of wack the reasons are numerous

1- You are too thin with BMI < 18, not enough body fat to insulate from cold temperature but also not eating enough slows down metabolism and not burning enough to generate bofy heat

2- Hypothyroidism, low thyroid hormone slows down metabolism and not enough heat generated by your body

3-chronic anemia, not enough iron in the blood, less cells circulating reduces the heating process of the tissu

4-poor circulation not enough blood circulating to your tissues and organe reduces the heating of those organes ( cardiovascular disease, Reynauld phenomenon is one example of circulation problem)

5-Sleep deprivation can throw of balance your thermostat which is your hypothalamus, stress and anxiety can slow activity in that area of your central nervous system causing bad temperature regulation

6-Chronic dehydration, you have to understand that organes get heated by blood supply, and lack water circulation is not as efficient, water carries heat and release it slowlykeeping your organe temperature at a comfortable zone

7-Diabetes : can lead to peripheral neurapothy which can lead to the feeling cold in addition to numbness and pain

in other words eat well, sleep well, exercise 3 times per week, drink a lot of fluid, and check with your Doctor

GOD BLESS

Considering you have full body cold intolerance, having thyroid function tests and checking a CBC to screen for anemia are warranted. I would also consider evaluation of the hypothalamus via pituitary lab tests and consider a brain MRI. Inactivity and/or low body fat are common factors which may cause cold intolerance - Response by David Douglas PA-C. Supervising Doctor is William E Hough.

This certainly may be Raynauds. I have seen bright red changes with temperature change as well. If you are in doubt as to the accuracy of your diagnosis I would seek out the advice of a second practitioner. There are blood studies that can be ran to look for additional reasons why you may be feeling cold all over. Checking the thyroid for hypothyroidism, checking the blood for anemia may be helpful.