Final answer:
Cortisol is the hormone that causes the allostatic load.
Step-by-step explanation:
The hormone that causes the allostatic load is cortisol. When a person experiences stress, the hypothalamus releases corticotropin-releasing factor, which triggers the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal glands to secrete cortisol into the bloodstream.