The correct answer is option 3: Insulin.

Insulin is a hormone that plays a crucial role in regulating blood glucose levels in the human body. It is produced by beta cells in the pancreas. Insulin acts on cells, particularly muscle, liver, and adipose (fat) cells, to facilitate the uptake of glucose from the bloodstream into the cells.

Option 1: GH, also known as growth hormone, is responsible for promoting growth, but it does not directly affect the uptake of glucose by cells.

Option 2: TSH, or thyroid-stimulating hormone, regulates the activity of the thyroid gland. It does not have a direct impact on glucose uptake.

Option 4: Cortisol, also known as the stress hormone, is involved in various functions, including metabolism. While cortisol can affect blood glucose levels, it primarily works by increasing glucose production in the liver rather than promoting glucose uptake by cells.

In conclusion, insulin is the hormone essential for the uptake of glucose by cells in the human body.