Hyperpituitarism (Overactive Pituitary Gland)

What is hyperpituitarism (overactive pituitary gland)?

When your pituitary gland is overactive, it releases excessive amounts of certain types of pituitary hormones into your bloodstream. A noncancerous (benign) tumor in the gland, called a pituitary adenoma, is usually the cause of this condition. An overactive pituitary gland can cause a variety of disorders that affect growth, metabolism, reproduction and other vital body functions.

What does the pituitary gland do?

The pituitary gland plays a major role in controlling how your body works. It’s a pea-sized, cherry-shaped endocrine gland located near the base of your brain. Endocrine glands release (secrete) hormones into your bloodstream that control your body’s functions. Your endocrine system affects almost every cell and organ in your body. Sometimes the pituitary is called the “master gland” because it controls the activity of other endocrine glands. Most importantly, it controls the activity of your thyroid gland, adrenal gland and gonadal glands (ovaries or testes).

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Think of your pituitary gland like a thermostat. The thermostat performs constant temperature checks in your home to keep you comfortable. It sends signals to your heating and cooling systems to turn up or down — and by how many degrees — to keep air temperatures constant. Your pituitary gland monitors your body functions in much the same way. Your pituitary gland sends signals to your organs and glands to tell them what functions are needed and when. The right settings for your body depend upon many things, including your sex, weight distribution and how active you are.

Blood vessels connect your pituitary gland to a part of your brain called the hypothalamus. Your brain tells your pituitary gland to increase or decrease the secretion of certain hormones.

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Your pituitary gland consists of three parts: the anterior, intermediate and posterior lobes.

Anterior lobe

Your anterior lobe makes up about 80% of your pituitary gland and releases these hormones:

• Adrenocorticotropic hormone (ACTH): This hormone causes your adrenal glands to produce steroid hormones, especially cortisol. Cortisol is the main stress hormone in your body, which keeps inflammation down and your blood pressure steady. You’re probably familiar with the role of cortisol in the “fight-or-flight” instinct.
• Growth hormone (GH): This hormone regulates your body’s growth (especially in children), metabolism and body composition (such as how much fat, muscle and fluids you have).
• Thyroid stimulating hormone (TSH): This hormone causes your thyroid gland to produce thyroid hormones that control how much energy you have.
• Gonadotropins — luteinizing hormone (LH) and follicle stimulating hormone (FSH): These hormones cause the ovaries and testicles to secrete sex hormones needed for reproduction.
• Prolactin: This hormone stimulates breastmilk production in people after they give birth.

Intermediate lobe

Your intermediate lobe secretes only one hormone:

• Melanocyte-stimulating hormone: This hormone affects skin pigmentation.

Posterior lobe

Your posterior lobe stores and releases two hormones that your hypothalamus produces:

• Antidiuretic hormone (ADH): This hormonecontrols water and electrolyte balance.
• Oxytocin: This hormone manages uterine contractions during childbirth and the production and release of breast milk.

What pituitary disorders are associated with hyperpituitarism?

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There are a number of adrenal disorders that can develop as a result of hyperpituitarism (overactive pituitary gland):

• Cushing’s syndrome (hypercortisolism): If your pituitary gland secretes too much adrenocorticotropic hormone (ACTH), your adrenal glands may release too much cortisol. Besides being a “stress hormone,” cortisol manages the metabolism of proteins, fats and carbohydrates. It’s also involved in your body’s inflammatory and immune responses.
• Acromegaly: This disorder is a rare but serious condition that happens when your body releases high levels of growth hormone (GH) into your bloodstream, leading your bones and tissues to grow in abnormal ways.
• Hyperthyroidism: If a pituitary tumor (adenoma) causes overproduction of thyroid stimulating hormone (TSH) (which is very rare), your thyroid gland will become hyperactive. This condition is also called overactive thyroid and can increase your metabolism, heartbeat rhythm and anxiety.
• Hypothyroidism: If a pituitary adenoma causes your pituitary gland to make too little thyroid stimulating hormone (TSH), your thyroid gland may become hypoactive. Hypothyroidism caused by a noncancerous (benign) pituitary tumor is rare, but it can occur.
• Prolactinoma: A benign tumor on your pituitary gland known as a prolactinoma may cause the gland to secrete too much prolactin. High levels of prolactin can disrupt normal reproductive function by interfering with hormones produced by the testicles or ovaries.

How common are hyperpituitarism (overactive pituitary gland) disorders?

Depending on the disorder, some are more common than others. Some of the most common conditions are:

• Small benign pituitary tumors (adenomas): These are fairly common. About 10,000 are diagnosed in the U.S. each year. They may secrete excess amounts of hormones or be nonsecreting and not cause any symptoms.
• Prolactinomas: Prolactinomas are the most common type of pituitary tumors, occurring in about 1 out of every 10,000 people. They’re more common in people assigned female at birth than people assigned male at birth.
• Cushing’s syndrome: Cushing’s syndrome is a relatively rare disorder that occurs mainly in adults between the ages of 20 and 50 years old.
• Acromegaly: Acromegaly is a rare disorder that occurs in only about 3 out of every 1 million people each year. It’s generally diagnosed in adults between the ages of 40 and 45.

Hyperpituitarism in children

Hyperpituitarism is rare in children. If it does occur, it typically results from pituitary microadenoma, a small (less than 10 millimeters), benign tumor. The most common pituitary adenoma found in childhood are prolactinomas, which occur in approximately half of all cases. Prolactinomas originate from stem cells of hormone-producing glands, which explains why they may secrete hormones. Several inherited syndromes — including multiple endocrine neoplasia type 1 (MEN1), Carney complex and familial isolated pituitary adenomas — appear to cause prolactinomas.

The disorders caused by prolactinomas depend on the sex and age of the child:

• Children assigned female at birth may experience delays in puberty, loss of monthly periods (amenorrhea) and other symptoms of hypogonadism (failure of the ovaries to function properly). They produce less estrogen.
• Children assigned male at birth are more prone to macroprolactinomas (large prolactinomas). Due to the size of macroprolactinomas, they tend to cause mass effect. This means the tumor presses on nerves and causes more neurological and ophthalmological issues (cranial nerve compression, headaches and vision loss). They can also experience puberty delays or growth issues.

Is hyperpituitarism (overactive pituitary gland) serious?

If left untreated, the conditions associated with hyperpituitarism can cause serious health problems. That’s why it’s important to talk to your healthcare provider if you experience symptoms of these disorders.

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