I am NOT a doctor but it sounds like an adrenal tumor cushings disease. It IS not deadly and once removed she would be 100% normal.. and the tsh number you gave is hyper thyroid...look into Cushings.
I did some brief reading and here are my thoughts: your daughter likely started off with hypothyroidism, or insufficient amounts of thyroid hormone in her body--so she may have been really fatigued, overweight, lacking an appetite, dry skin, thin hair, etc. This would mean her pituitary detected the low quantities of thyroid hormones in her bloodstream, and began secreting more thyrotropin (TSH) to try and flog her thyroid into producing more of the necessary hormones (a negative-feedback system our body has). The cells that produce this thyrotropin, called thyrotrophs, underwent hyperplasia (aka proliferation beyond what is normal), resulting in enlargement of her pituitary gland...or pituitary hyperplasia. Somewhere along the signal cascade, this definitely caused the release of a lot more TSH, causing the thyroid to switch into overdrive, where it was producing too many thyroid hormones and causing her to go hyperthyroid. Now, her TSH is dropping because she has too many thyroid hormones in her body, causing her to become almost hyperactive--leading to headaches, weight loss, jitteryness/body tremors, being cold, etc. The high-normal FT3 and FT4 support this theory.
As for the "homogeneous" comment in her radiology report, I wonder if this has something to do with the signal intensity ratio when the pituitary gland is in a euthyroid state as opposed to a hyperthyroid or hypothyroid state...though I'm not really sure--definitely ask about this, because I know the bottom (right) of the pituitary gland should light up when contrast is added, but the rest of the gland should look homogeneous and non-enhancing with contrast addition, as far as I know. But the "prominent" part refers to her pituitary gland being larger in size than it should be, and the "convex upper border" likely refers to the top (almost top right, depending on how it's positioned since it varies slightly from person to person) of her pituitary as curving outward, rather than curving slightly inward, as pituitary glands tend to do. Think of the shape of a lima bean, as opposed to an egg.
The seizures are probably a result of the pituitary gland being larger than normal, which may be infringing on nearby parts of your daughter's brain that it shouldn't be, and maybe even putting pressure on some areas.
I'm no doctor, but I tried! I hope this helps, and I hope your daughter gets the treatment she deserves so she can enjoy her high-school years. =)
Did her neurologist or endocrinologist comment on the results, yet?