The thyroid and addison's are unrelated except that they are both auto-immune and endocrine. Plenty of people get either one separately.
I would call around and try to find an endo that treats and tests for Addison's disease. The blood sugar issues can be related to the cortisol as cortisol can be effected by it. However usually high cortisol leads to high glucose so that is unusual. So the ups and downs are cortisol swings perhaps. You are at risk, perhaps for an adrenal crisis and need to get a competent doctor. You need a stim test.
I have an apt with a new endo. I got my urine test back which checked for Catecholamines, metanepharines, and creatinine and they were all with in normal range. I am very worried about adrenal crisis like you had mentioned. Curent endo wants me to repeat tests : CMP, H1AC, Cortisol. She also wants me to get ACTH which i think is the stim test. Can you tell me more about adrenal crisis. I am so nervous to be alone now...
You can google adrenal crisis and get the symptoms - prevention is key. Just so you know, I have no adrenals, and I manage. If you start to feel bad, make sure you get salt and fluids in you and get to an ER if you need to.
CMP is general stuff, H1ac is for blood sugar and cortisol is well... ACTH is just ACTH - the stim test is very involved. ACTH is very fussy - read up on how it is done and ask the tech to do it properly so it does not degrade.
I think you may have Adrenal Fatigue Syndrome:
Progressively increasing lethargy and lack of energy.
Increased effort needed just to perform daily tasks.
Decreased ability to handle stress.
Tendency to gain weight, coupled with an inability to lose it, especially settling around the waist.
Frequent bouts of influenza and other respiratory diseases, with symptoms lasting longer than usual.
Trembling under pressure.
Reduced sex drive.
Tendency to feel light-headed especially when rising from a horizontal position.
Inability to remember things.
Lack of energy in the morning and in the afternoon between 3:00 and 5:00 PM.
Tendency to feel better suddenly for a brief period after a meal.
Often feels tired between 9:00 and 10:00 PM, but resists going to bed.
Difficulty getting out of bed in the morning.
Once out of bed, has a need for coffee or other stimulants to get going.
Cravings for salty, fatty, and high protein food such as meat or cheese.
For women, increased symptoms of PMS and irregular menstrual bleeding, with days of heavy flow that stops (or nearly stops) on day 4, only to resume on days 5 or 6 of the menstrual cycle.
Pain in the upper back or neck for no apparent reason.
Tendency to feel better on vacation and when stress is relieved.
Food and or inhalant (airborne) allergies.
Dry and thin skin.
Low body temperature.
Unexplained hair loss.
Alternating constipation and diarrhea.