Thyroid function tests are blood tests that check the levels of the hormones (chemicals) made by the thyroid gland. Some thyroid function tests also check the level of a hormone made by the pituitary gland in the brain, which acts on the thyroid gland.hyroid function tests are blood tests that check the levels of the hormones (chemicals) made by the thyroid gland. Some thyroid function tests also check the level of a hormone made by the pituitary gland in the brain, which acts on the thyroid gland.
Yes, high intakes of some forms of vitamin A can be harmful. Getting too much preformed vitamin A (usually from supplements or certain medicines) can cause dizziness, nausea, headaches, coma, and even death. High intakes of preformed vitamin A in pregnant women can also cause birth defects in their babies.
It's also in most fruits and vegetables, mostly in the form of carotenoids. It's important during pregnancy not to get too much of the preformed vitamin A, which in high doses can cause birth defects and liver toxicity.itamin A in your pregnancy diet. In this article. 1  Why you need vitamin A during pregnancy. 2  Understanding vitamin A. 3  How much vitamin A you need.