Final answer:
The pituitary hormone that stimulates the breakdown of stored fats is Growth Hormone (GH), which promotes lipolysis, the process of breaking down triglycerides to release fatty acids.
Step-by-step explanation:
The pituitary hormone responsible for stimulating the breakdown of stored fats and the release of fatty acids into the blood is Growth Hormone (GH). GH promotes the process known as lipolysis, whereby triglycerides are broken down to release fatty acids as an energy source for the body's tissues. Although the adrenocorticotropic hormone (ACTH) is involved in the stress response and stimulates the release of glucocorticoids, which can influence metabolism, it is not directly responsible for this action.