The Pituitary Gland: How It Controls the Endocrine System

The pituitary gland is tiny, but its influence reaches the thyroid, adrenal glands, reproductive system, growth, lactation and water balance. Calling it the “master gland” is useful shorthand, although it can give the wrong impression that the pituitary works independently. Much of its activity is directed by the hypothalamus, and the hormones released by target organs feed information back into the system.

The useful way to learn the pituitary is not as a long list of hormones. Start with its position, separate the anterior and posterior lobes, then follow where each hormone comes from and where it acts.

Where is the pituitary gland?

The pituitary sits at the base of the brain within the sella turcica, a depression in the sphenoid bone. The pituitary stalk connects it with the hypothalamus above. The optic chiasm lies just superior to the sella, while the cavernous sinuses lie laterally. Those close anatomical relationships become clinically important when a pituitary lesion enlarges. Compression of the optic chiasm can disturb the visual fields, classically producing loss of temporal vision on both sides, although the exact pattern varies with the relationship between the lesion and the visual pathways.

Although we talk about one pituitary gland, its two main lobes work quite differently. The anterior pituitary, or adenohypophysis, is glandular tissue that synthesises and secretes several hormones. The posterior pituitary, or neurohypophysis, is neural tissue connected directly to hypothalamic neurons.

The hypothalamus and anterior pituitary work as a system

The anterior pituitary does not simply decide which hormones to release. Hypothalamic releasing and inhibiting hormones enter a specialised network of blood vessels called the hypophyseal portal system. This carries them directly to cells in the anterior pituitary.

Those signals regulate the release of six hormones that students commonly need to know: thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), growth hormone (GH), follicle-stimulating hormone (FSH), luteinising hormone (LH) and prolactin.

TSH links the pituitary with the thyroid

Thyrotropin-releasing hormone (TRH) from the hypothalamus stimulates the anterior pituitary to release thyroid-stimulating hormone. TSH then acts on the thyroid gland, promoting the production and release of thyroid hormones.

As circulating thyroid hormone concentrations rise, they feed back to the hypothalamus and pituitary and reduce further stimulation. This negative feedback relationship is why thyroid blood results are usually interpreted together rather than treating a TSH result as an isolated number.

ACTH links the pituitary with the adrenal cortex

Corticotropin-releasing hormone (CRH) from the hypothalamus stimulates release of adrenocorticotrophic hormone from the anterior pituitary. ACTH acts principally on the adrenal cortex and is an important regulator of cortisol secretion.

Cortisol then contributes to negative feedback at the hypothalamus and pituitary. Thinking in terms of this axis helps when learning disorders in which the problem can arise at different levels rather than simply memorising whether a hormone is “high” or “low”.

FSH and LH connect the pituitary with reproductive function

Follicle-stimulating hormone and luteinising hormone are released by gonadotroph cells in response to pulsatile gonadotropin-releasing hormone (GnRH) from the hypothalamus. Their effects differ with reproductive physiology, but together they are central to ovarian follicle development, ovulation, sex steroid production and testicular function.

This is one reason pituitary disease can present through changes that may initially seem unrelated to the brain, including menstrual disturbance, fertility problems or altered sexual function.

Growth hormone does more than control height

Growth hormone is released from somatotroph cells. Its secretion is stimulated by growth hormone-releasing hormone and inhibited by somatostatin. Growth hormone acts directly on some tissues and also stimulates production of insulin-like growth factor 1 (IGF-1), particularly by the liver.

Its effects include growth during childhood and regulation of metabolism throughout life. Excess or deficiency therefore produces different clinical effects depending on age and the underlying cause.

Prolactin is regulated differently

Prolactin is produced by lactotroph cells of the anterior pituitary and supports milk production. Unlike many of the other anterior pituitary hormones, its control is dominated by inhibition. Dopamine released by the hypothalamus normally suppresses prolactin secretion.

This becomes clinically useful when thinking about medicines or lesions that interfere with dopamine signalling. Removing that inhibitory influence can allow prolactin concentrations to rise.

The posterior pituitary is different

The posterior pituitary is often taught alongside the anterior pituitary, but there is an important distinction: it does not synthesise its two principal hormones.

Arginine vasopressin (AVP), also commonly called antidiuretic hormone (ADH), and oxytocin are synthesised by neurons in the hypothalamus. They travel down axons through the pituitary stalk and are stored in nerve terminals in the posterior pituitary until they are released into the circulation.

AVP is central to the regulation of water balance. In the kidney it acts mainly through V2 receptors in the collecting ducts, promoting insertion of aquaporin-2 water channels and increasing water reabsorption. Oxytocin has important roles in uterine contraction and milk ejection. Both hormones therefore enter the circulation from the posterior pituitary, but they are synthesised in hypothalamic neurons rather than in the posterior lobe itself.

Negative feedback keeps the axes regulated

Several pituitary systems are organised as endocrine axes. The hypothalamus signals the pituitary, the pituitary stimulates a target organ, and hormones produced further along the pathway feed back to modify further secretion.

This is more useful than memorising arrows on a diagram because it helps explain blood results. A low target-organ hormone with an appropriately raised pituitary hormone suggests a different level of dysfunction from a low target-organ hormone accompanied by an inappropriately low or normal pituitary signal. Interpretation still depends on the particular axis, the clinical picture, medicines and local investigation pathways.

Why pituitary anatomy matters clinically

A pituitary disorder can affect one hormone, several hormones or surrounding structures. Symptoms therefore depend on what is being produced in excess, what is deficient and whether a lesion is large enough to affect nearby anatomy.

For a nurse, the presentation may appear through another body system: unexplained changes in fluid balance, menstrual disturbance, altered growth, symptoms of adrenal or thyroid dysfunction, lactation outside the expected context, or visual symptoms. The physiology helps connect those apparently separate findings.

One particularly useful distinction is the posterior pituitary pathway. Reduced AVP activity can impair the kidney's ability to conserve water, producing polyuria and polydipsia. In current clinical terminology this disorder is increasingly referred to as arginine vasopressin deficiency, although the older term central diabetes insipidus is still widely encountered. The underlying physiology is the same: insufficient effective AVP activity means less water is retained by the kidneys.

Putting the pituitary together

The pituitary earns its reputation because several major endocrine pathways pass through it, but the hypothalamus remains central to its control. The anterior lobe responds largely to hypothalamic signals delivered through the portal circulation and produces its own hormones. The posterior lobe receives hormones made by hypothalamic neurons and stores and releases them.

Once that anatomical difference is clear, the individual hormones become easier to place. Instead of learning eight disconnected names, you can follow a signal from the hypothalamus, through the pituitary and towards its target tissue, then consider how feedback closes the loop.

References

Lechan, R.M. and Toni, R. (2016) ‘Functional Anatomy of the Hypothalamus and Pituitary’, in Feingold, K.R. et al. (eds.) Endotext. South Dartmouth (MA): MDText.com, Inc. NCBI Bookshelf.

Lim, C.T. and Khoo, B. (2025) ‘Normal Physiology of ACTH and GH Release in the Hypothalamus and Anterior Pituitary in Man’, in Feingold, K.R. et al. (eds.) Endotext. South Dartmouth (MA): MDText.com, Inc. NCBI Bookshelf.

Scott, I.S., Chattopadhyay, A. and Ansorge, O. (2025) ‘Development and Microscopic Anatomy of the Pituitary Gland’, in Feingold, K.R. et al. (eds.) Endotext. South Dartmouth (MA): MDText.com, Inc. NCBI Bookshelf.

Rawindraraj, A.D., Basit, H. and Jialal, I. (2023) ‘Physiology, Anterior Pituitary’, StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf.

Patel, H., Jessu, R. and Tiwari, V. (2023) ‘Physiology, Posterior Pituitary’, StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf.

University College London Hospitals NHS Foundation Trust (2026) ‘Endoscopic transsphenoidal pituitary surgery’. UCLH.