Final answer:
Panhypopituitarism is the condition with below normal secretion of all pituitary hormones, which is the correct answer to the student's question.
Step-by-step explanation:
The question asks about a disease characterized by below normal secretion of all the pituitary gland hormones. The correct answer to this question is D) Panhypopituitarism. Panhypopituitarism is a condition characterized by inadequate secretion of hormones by the pituitary gland. This contrasts with disorders such as Addison's disease, which involves hyposecretion of cortisol and potentially mineralocorticoids generally due to autoimmune causes, infections, or pituitary damage, and Cushing's disease, which is the result of hypersecretion of cortisol most commonly caused by a pituitary tumor. Diabetes insipidus involves underproduction of the antidiuretic hormone (ADH) leading to chronic dehydration, but does not affect all pituitary hormones.