If the thyroid and parathyroid glands are surgically removed, which of the following would go out of balance without replacement therapy?

A. Hydrostatic pressure of capillary blood: This pushes water out of capillaries into the interstitial space-it's the main driver of filtration at the arterial end of capillaries.
B. Osmotic pressure of plasma proteins: This pulls water back into capillaries, opposing outward flow.
C. Hydrostatic pressure of interstitial fluid: This would oppose outward filtration if significant, but it's usually low.
D. Intracellular hydrostatic pressure: This is not relevant to capillary filtration, which occurs between plasma and interstitial fluid.

A. Gastrin: G cells secrete gastrin, a hormone that stimulates parietal cells to produce hydrochloric acid and promotes gastric motility. It is released in response to food components like peptides, caffeine, and a rise in pH.
B. Pepsin: Pepsin is an enzyme that digests proteins, but it is secreted as pepsinogen by chief cells, not G cells.
C. Ghrelin: Ghrelin is a hunger-stimulating hormone, secreted primarily by cells in the stomach fundus, not by G cells.
D. Hydrochloric acid: Hydrochloric acid is secreted by parietal cells, not G cells.