Goiters may occur due to iodine insufficiency, but other causes are possible. Which of the following would NOT tend to result in increased size of the thyroid gland? A. High levels of thyrotropin releasing hormone.
B. High levels of thyroid stimulating hormone.
C. High levels of thyroxin and triiodothyronine.
D. All of the above would tend to increase the size of the thyroid gland.
E. None of the above would tend to increase the size of the thyroid gland.

Option A

Explanation:

Thyroid is primarily caused by lack of iodine but there are other reasons as well that lead to increased size of the thyroid gland. Some of these reason is

a) over- or underproduction of thyroid hormones

b) Nodules in the glans

Some times, due to overstimulation immune system itself attack the thyroid gland thereby producing excess thyroxine and hence causing  the thyroid to swell

Thus, Option A is correct

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!