Adrenocorticotropic hormone (ACTH) is a hormone from the anterior pituitary that tells the adrenal cortex to release cortisol. In Anatomy and Physiology I, it shows how the hypothalamus, pituitary, and adrenal glands work together in the stress response.
Adrenocorticotropic hormone, or ACTH, is a peptide hormone released by the anterior pituitary gland. In Anatomy and Physiology I, you usually meet it as the signal that tells the adrenal cortex to make and release cortisol.
ACTH sits in the middle of the hypothalamic-pituitary-adrenal, or HPA, axis. The chain starts when the hypothalamus releases corticotropin-releasing hormone, called CRH. CRH tells the anterior pituitary to secrete ACTH into the blood, and ACTH then acts on the adrenal cortex, especially the outer part of the adrenal gland.
The main result is cortisol release. Cortisol helps the body respond to stress by raising available energy, supporting blood pressure, and affecting metabolism. It also feeds back to the hypothalamus and pituitary, which helps slow down further CRH and ACTH release once cortisol levels are high enough. That negative feedback loop is a big reason the endocrine system can stay stable instead of overreacting.
ACTH is not a storage hormone. It is released in pulses, and its secretion follows a daily rhythm, usually peaking in the early morning and falling later in the day. That rhythm is why cortisol levels are also higher in the morning. If you are looking at hormone timing on a graph or in a lab question, ACTH often rises before cortisol does.
A helpful way to think about ACTH is as a messenger, not the final answer. It does not directly create the stress response by itself. It signals the adrenal cortex to produce hormones that change how your body uses fuel, handles stress, and maintains homeostasis. That makes it a good example of how one gland can control another gland through a hormone relay.
ACTH shows how endocrine glands communicate in a step-by-step pathway instead of working alone. In Anatomy and Physiology I, that makes it a useful example for tracing cause and effect from the hypothalamus to the pituitary to the adrenal cortex.
It also connects two big course ideas at once: homeostasis and feedback control. When cortisol rises, it helps the body cope with stress, but it also sends signals back to the brain and pituitary to limit more ACTH release. If you can explain that loop, you are already using the same logic that shows up in many endocrine questions.
ACTH matters in adrenal gland topics too, because it helps explain why the adrenal cortex changes hormone output. When ACTH is too high or too low, the body can show signs of adrenal disease, such as cortisol imbalance, fatigue, or abnormal stress handling. That is why ACTH comes up in hormone testing and case studies, not just in memorization lists.
It also gives you a clean example of how hormone timing matters. The daily rhythm of ACTH secretion can help explain why cortisol is not constant across the day. In practical terms, that means you can use ACTH to interpret hormone charts, compare normal and abnormal patterns, and explain why the endocrine system is more dynamic than a simple on-off switch.
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Visual cheatsheet
view galleryCorticotropin-Releasing Hormone
CRH is the hypothalamic hormone that comes before ACTH in the HPA axis. If CRH is the first signal, ACTH is the second, carrying the message from the brain to the anterior pituitary and then toward the adrenal cortex. When you trace the pathway, CRH tells you where the stress response starts.
Cortisol
Cortisol is the main hormone released after ACTH stimulates the adrenal cortex. ACTH is the signal, while cortisol is one of the major results you track in the body. If a question asks about stress, blood glucose, or feedback inhibition, cortisol is often the hormone doing the downstream work.
Hypothalamic-Pituitary-Adrenal Axis
The HPA axis is the full communication pathway that includes the hypothalamus, pituitary gland, ACTH, and adrenal cortex. ACTH is one step in that chain, so it is not the whole system. When you understand ACTH, you can explain how the entire axis responds to stress and resets itself through negative feedback.
Adrenal Insufficiency
Adrenal insufficiency is a condition where the adrenal glands do not make enough hormones, often including cortisol. ACTH levels can help you figure out where the problem is coming from, because the pituitary may increase ACTH when cortisol is low, or ACTH may be low if the pituitary is the issue. That makes ACTH useful in diagnosing hormone imbalance.
A quiz question might ask you to order the HPA axis, label a hormone pathway, or explain what happens when cortisol levels rise. In that kind of item, you would identify ACTH as the anterior pituitary hormone that stimulates the adrenal cortex, then connect it to CRH and cortisol. If you get a case study about stress, fatigue, or abnormal morning hormone levels, ACTH is one of the first hormones you should consider.
In a lab or data-interpretation problem, you may be given a graph showing a morning peak in ACTH followed by a cortisol peak. Your job is to read the timing and explain the feedback loop, not just name the hormone. If the question mentions adrenal disease, ACTH levels can help you decide whether the problem is more likely in the pituitary or the adrenal glands.
ACTH and cortisol are easy to mix up because they work in the same stress pathway, but they are not the same thing. ACTH is the signal from the anterior pituitary, while cortisol is the hormone released by the adrenal cortex after that signal arrives. If you are tracing the pathway, ACTH comes first and cortisol comes after.
Adrenocorticotropic hormone is an anterior pituitary hormone that stimulates the adrenal cortex to release cortisol.
ACTH is part of the hypothalamic-pituitary-adrenal axis, so it links the hypothalamus, pituitary gland, and adrenal glands.
Its release is triggered by corticotropin-releasing hormone from the hypothalamus and controlled by negative feedback from cortisol.
ACTH secretion follows a daily rhythm, with higher levels in the early morning and lower levels later in the day.
In Anatomy and Physiology I, ACTH often shows up in hormone pathways, feedback loops, and adrenal disorder case questions.
Adrenocorticotropic hormone, or ACTH, is a peptide hormone made by the anterior pituitary gland. It signals the adrenal cortex to release cortisol, especially during stress. In A&P, it is a core example of endocrine communication and feedback control.
ACTH is the middle step in the hypothalamic-pituitary-adrenal axis. The hypothalamus releases CRH, CRH tells the anterior pituitary to release ACTH, and ACTH tells the adrenal cortex to produce cortisol. Cortisol then feeds back to reduce further release of CRH and ACTH.
No. ACTH is the hormone signal from the anterior pituitary, while cortisol is the hormone made by the adrenal cortex after ACTH acts on it. A good shortcut is that ACTH tells the body to make cortisol, but ACTH is not the stress hormone itself.
ACTH levels can help show whether a hormone problem starts in the pituitary or in the adrenal glands. If cortisol is low, ACTH may be high if the pituitary is trying to compensate, or low if the pituitary is not signaling properly. That is why ACTH is useful in endocrine case analysis.