You’ve probably heard of the Pituitary Gland, but do you know what it does? Do you know where it’s located? Do you know what functions it controls? Did you know it secretes (releases) eight different hormones that control the functioning of several bodily organ systems? Did you know these hormones determine your height, weight, fertility, energy level, and hydration status among other things? Well, if you don’t know the answer to these questions, this blog will attempt to provide some answers.
The pituitary gland is the “master” control center of the endocrine system. It sits in a bony cup-like area called the sella turcica in the floor of the skull. The pituitary attaches to the base of the brain by a stalk, and in the stalk are nerves and blood vessels that allow the pituitary to interface with the brain. The stalk is surrounded by the main nerves to the eyes, the optic nerves. The endocrine system is a group of glandular structures throughout the body that produce hormones. Hormones are chemical substances that function like “messengers” and deliver a stimulus to the organ they target. More detail on hormones later.
The pituitary is no larger in diameter than a dime. It is separated into two parts, the anterior lobe and the posterior lobe, each of which has specific functions. The cells of the pituitary gland produce hormones that are delivered to the glandular structures of the endocrine system and cause each target organ to carry out its function.
The 6 hormones produced in the anterior lobe of the pituitary are the following:
Growth Hormone (GH)
Thyroid Stimulating Hormone (TSH)
Prolactin (PRH)
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Adrenocorticotropic Hormone (ACTH)
The 2 hormones produced in the posterior lobe of the pituitary are the following:
Oxytocin
Vasopressin/Antidiuretic Hormone (ADH)
So you can see, the pituitary gland “runs the show.” It is the most important part of the endocrine system because it directs the function of so many other parts of the system. Each of the hormones has a specific function that is important for the metabolic balance of the entire body. The organs of the endocrine system are the ovaries, testes, adrenals, pancreas, thyroid, and the pituitary with the pituitary being the one that causes all of the others to work. The functions of the hormones secreted by the anterior lobe of the pituitary are numerous and result in the following changes in the body:
Growth Hormone (GH): regulates body size, shape, and physical development by stimulating muscle formation, bone growth, and fat deposition. Its principal targets are bone and muscle, but GH acts on almost every cell in the body.
Thyroid Stimulating Hormone (TSH): Stimulates the thyroid gland to produce the chemical substances T3 and T4 which are the main thyroid hormones. The thyroid then affects weight, appetite, energy, memory and thinking, and strength.
Prolactin (PRH): Stimulates the breasts and gonads to cause the mammary glands to grow and produce breast milk after pregnancy.
Follicle-Stimulating Hormones (FSH): Stimulates the ovaries to produce and release eggs (ova and wovulation) and the testes to produce sperm (spermatogenesis). It also produces estrogen and testosterone, the “sex hormones.”
Luteinizing Hormone (LH): Stimulates the ovaries and triggers ovulation and testosterone release. It aids in protecting and maturing a fertilized ovum.
Adrenocorticotropic Hormones (ACTH): Stimulates the adrenal glands to produce cortisol and other hormones, especially epinephrine and norepinephrine during stress.
The functions of the two hormones produced by the posterior lobe of the pituitary are the following:
Oxytocin: Is released when a pregnant woman has reached full term, and it stimulates uterine contractions, initiates labor, enables birth of the infant. Immediately after delivery, oxytocin causes the uterus to contract to prevent bleeding.
Vasopressin, Anti-Diuretic Hormone (ADH): Stimulates the kidney tubules to reabsorb water back into the blood stream, maintains water balance in the body, and keeps the individual from becoming dehydrated. It regulates the amount of water excreted by the kidneys.
The Pituitary has multiple cell types within the gland. Thus, it has multiple and varied functions. The hormones produced target the organs of the endocrine system. Because the pituitary controls multiple other organs, problems with the pituitary can occur from producing too much hormone or too little. Situations in which too much hormone is produced are usually caused by a benign tumor of the cells in the pituitary.
Scenarios where too much hormone is produced are the following:
Excess Growth Hormone—if excess GH begins in childhood, while the bones are still growing, the result is Gigantism where a child grows to be an 8-feet tall adult. If excess GH begins when bone growth is complete, the result is acromegaly where the bones don’t get longer but broader and thicker.
Excess TSH—This will overstimulate the thyroid causing hyperthyroidism—symptoms are tremor, rapid heart rate, hyperactive reflexes, excess energy, and goiter (enlarged thyroid gland).
Excess ACTH—This overstimulates the adrenals to over-produce cortisol resulting in Cushing’s Syndrome—obesity, Buffalo hump on the upper back, abdominal stretch marks (striae), increased fracture risk, diabetes (high blood sugar), and high blood pressure.
Excess Prolactin—causes abnormal periods, sexual dysfunction, and galactorrhea—secretion of breast milk in men or in non-pregnant women. Infertility.
Situations where too little pituitary hormone is produced occur when vascular disease or blood loss from hemorrhage prevents adequate blood supply from reaching the pituitary. The gland shuts down causing lesser amounts of hormones to be produced. Those conditions are:
Low GH—causes poor growth rate, small stature.
Low TSH—causes underactive thyroid with fatigue, weight gain, sluggishness
Low ACTH—causes adrenal insufficiency, ie. Addison’s disease—low BP, dark skin pigment, fatigue, nausea, low blood sugar, and dizziness.
Low FSH, LH—causes an absence of periods and ovulation—infertility
Low ADH—causes diabetes insipidus—the excessive elimination of very dilute urine to the point of dehydration.
Pituitary tumors make up 15% of all “brain” tumors. Malignant pituitary tumors are nearly non-existent, however. The pituitary is a “glandular” structure. Benign tumors of the pituitary cells are thus called adenomas, either microadenomas or macroadenomas. If they need treatment, they are either stereotactically irradiated or removed trans-nasally through the sphenoid sinus.
Now you know where the pituitary gland is and what it does. It has multiple important involuntary functions we all take for granted and don’t give a second thought. However, the pituitary gland is about as important as any other organ in the body.
References: https://www.hopkins.medicine.org/health/conditions-and-diseases/the-pituitary-gland.
El Stayed SA, Fahmy MW, Schwartz J. Physiology, Pituitary Gland 2023 May 1. NCBI Bookshelf NLM/NIH.
Foulad A, Meyers AD. Pituitary Gland Anatomy 2015 July 29; https://www.medscape.com/article/1899167-overview.
What is the pituitary gland? Univ of Chicago Medicine.
