Some antibodies against foreign antigens can react to similar self-antigens, causing an autoimmune disease.

A. The location of the target cells in the body:While the anatomical location of cells determines which tissues are exposed to circulating hormones, responsiveness is not dictated by location alone. Only cells with the appropriate receptors will respond.

B. The location of the gland that secretes the hormone:The position of the endocrine gland affects hormone distribution through the bloodstream but does not determine whether a cell is responsive. Responsiveness depends on receptor expression on the target cell.

C. The presence of a receptor for that particular hormone:A cell is responsive to a hormone only if it has specific receptors for that hormone. The binding of the hormone to its receptor triggers intracellular signaling pathways, leading to a physiological response.

D. The chemical properties of the hormone:The chemical nature of a hormone (e.g., peptide or steroid) affects how it interacts with receptors and enters cells, but it does not determine whether a cell is responsive; receptor presence is the key factor.

E. The site where the hormone is secreted:The secretion site influences how quickly the hormone reaches target cells, but a cell cannot respond without the appropriate receptor, making the secretion site irrelevant for responsiveness.

A. Oxytocin (OT):The posterior pituitary stores and secretes oxytocin, which is produced by the hypothalamus. Oxytocin stimulates uterine contractions during labor and milk ejection during breastfeeding, acting as a neurohormone released into the bloodstream.

B. Growth hormone (GH):GH is secreted by the anterior pituitary, not the posterior. It regulates growth, protein synthesis, and metabolism throughout the body.

C. Prolactin (PRL):Prolactin is also produced by the anterior pituitary. Its main function is to stimulate milk production in the mammary glands after childbirth.

D. Thyroid hormone (TH):Thyroid hormone is secreted by the thyroid gland, not the pituitary. It regulates metabolism, growth, and development in various tissues.

E. Adrenocorticotropic hormone (ACTH):ACTH is produced by the anterior pituitary and stimulates the adrenal cortex to secrete glucocorticoids, particularly cortisol. It is not stored or secreted by the posterior pituitary.