What Is Hypopituitarism?

Hypopituitarism is a rare disorder that causes the decreased production of one or more of the nine hormones produced by the pituitary gland. The signs and symptoms of hypopituitarism can vary by the hormones affected and may include everything from chronic fatigue and growth impairment to sexual dysfunction and the inability to produce breast milk.

The cause of hypopituitarism may be something you are born with or something that has directly damaged the pituitary gland (such as brain trauma, infection, or a tumor). The diagnosis can usually be made with blood tests and imaging studies. Hypopituitarism can often be treated with hormone replacement therapy.

Types of Hypopituitarism

The pituitary gland, sometimes referred to as the "master gland," is a pea-sized organ located near the base of the brain. Its role is to either synthesize and/or secrete hormones that regulate bodily functions. The pituitary gland itself is divided into two lobes—the anterior (front) lobe and the posterior (back) lobe—each of which has different functions. Hypopituitarism can be broadly classified by the lobe affected:

Anterior lobe hypopituitarism is characterized by decreases in the hormones produced and secreted by the anterior pituitary gland. These include:

• Adrenocorticotrophic hormone (ACTH), whose role is to stimulate the production of the stress hormone cortisol in the adrenal gland
• Follicle-stimulating hormone (FSH), which stimulates the growth of ovarian follicles during the menstrual cycle
• Growth hormone (GH), which stimulates growth in all tissues of the body, including bone
• Luteinizing hormone (LH), which triggers ovulation in women and stimulates the production of testosterone in men
• Melanocyte-stimulating hormone (MSH), which stimulate the production of the protective pigment melanin found in skin cells
• Prolactin (PRL), which direct the body to make breast milk when a woman is pregnant or breastfeeding
• Thyroid-stimulating hormone (TSH), which regulates the production of thyroid hormones

Posterior lobe hypopituitarism is charactered by decreases in hormones produced by the hypothalamus but secreted by the posterior pituitary gland:

• Anti-diuretic hormone (ADH), which regulates how much water your kidneys conserve or release
• Oxytocin, which helps induce labor contractions during pregnancy and also promotes breast milk production after birth

Hypopituitarism Symptoms

The symptoms of hypopituitarism can vary by the portion of the gland affected, the degree of hormonal impairment, and the age of an affected individual. In some cases, the effects may be subtle or and easily attributed to other conditions. At other times, the symptoms may be profound and debilitating.

Causes

The causes of hypopituitarism can be broadly classified as being either congenital (occurring before or at the time of birth) or acquired (occurring after birth).

Congenital

Congenital hypopituitarism may be the result of a genetic mutation that affects the normal development of the pituitary gland during the embryo stage. There are no less than 25 mutations known to cause pituitary deficiency, including five known as combined pituitary hormone deficiency (CPHD) 1 through 5.

The majority are mutations passed from parents to child in an autosomal recessive pattern, meaning that both parents must contribute a CPHD mutation in order for the disease to manifest.

Among the rare genetic syndromes associated with hypopituitarism are:

• Bardet-Biedl syndrome, which affects multiple body parts and organs
• Kallman syndrome, which affects sex hormone production
• Prader-Willi syndrome, which can lead to short stature, obesity, and intellectual disabilities

Congenital hypopituitarism can also occur at the time of birth due to pregnancy complications, including preterm birth, severe maternal anemia, pregnancy-induced hypertension, placental abruption, and severe blood loss during the delivery (Sheehan syndrome).

Acquired

Acquired causes are those in which the pituitary gland is directly or indirectly damaged either by trauma, infection, disease, or certain medical treatments. Common examples include:

• Traumatic brain injury (including subcranial hemorrhage)
• Pituitary adenoma (pituitary tumor)
• Brain tumor (including craniopharyngioma, meningioma, and glioma)
• Neurosurgery complications
• Hypophysitis (inflammation of the pituitary gland)
• Cancer metastasis (in which cancer spreads from another part of the body)
• Radiation therapy
• Sarcoidosis (an inflammatory disease causing the formation of granular lumps)
• Encephalitis (inflammation of the brain)
• Meningitis (inflammation of the tissue surrounding the brain and spinal cord)
• Hemochromatosis (iron overload)

In some cases, the cause of hypopituitarism is unknown. Doctors refer to this as idiopathic hypopituitarism.

Diagnosis

The diagnosis of hypopituitarism is based primarily on blood tests but may also involve imaging studies to look for evidence of pituitary damage or deformity.

Chief among these are blood tests that measure the amount of the pituitary hormone in a sample of blood. This is not always as straightforward as it sounds. Deficiencies can be diagnosed in one of two ways:

• Basal tests can detect hormone deficiencies based on a single test value. LH, FSH, prolactin, and TSH are all measured in this way. The blood is usually taken in the morning when hormone production is at its lowest.
• Dynamic tests are those in which hormone levels are measured after a drug has been administered to stimulate the hormone under investigation. ADH, GH, and ACHT are measured in this way.

Imaging studies may also be used to detect a pituitary tumor or other pituitary gland problems. The two most commonly used are:

• Computed tomography (CT), in which a series of X-rays are composited in a computer to create three-dimensional "slice" of the pituitary gland
• Magnetic resonance imaging (MRI), which uses powerful magnetic and radio waves to create highly detailed images of soft tissue

If a genetic cause is suspected, specialized genetic testing may be performed. These are typically ordered when rare disorders like Prader-Willi syndrome are suspected and/or there is a family history of hypopituitarism.

Differential Diagnoses

Because the cause of hypopituitarism is sometimes difficult to pinpoint, the doctor will investigate other causes in the differential diagnosis. These include other diseases associated with hormonal deficiencies, including:

• Addison's disease (an adrenal gland disorder)
• Primary hypothyroidism (in which the problem is related to the thyroid gland)
• Primary hypogonadism (in which the problem originates in the testes)
• Primary ovarian insufficiency (in which the problem originates in the ovaries)
• Polyglandular autoimmune syndrome (in which the immune systems attacks health glandular tissue)

Treatment

In most cases, people with hypopituitarism can be treated with lifelong hormone replacement therapy (HRT). Depending on the deficiency, a number of synthetic or natural hormones may be prescribed in pill, patch, or injectable form.

Some of the drugs used in HRT directly replace the depleted hormone. Others treated the so-called effector gland, meaning the gland that is directly stimulated by a pituitary hormone. (Examples include the thyroid gland which is regulated by TSH or the ovaries which are influenced by FSH and LH.)

Among the drugs commonly used in HRT for hypopituitarism:

• Hydrocortisone is a synthetic form of cortisol, taken by mouth, that is used to treat an ACTH deficiency.
• Estradiol is a synthetic form of estrogen, delivered in tablets or patches, that treats female hypogonadism caused by an LH or FSH deficiency. Progestin, a synthetic form of progesterone, is also sometimes used to prevent unwanted effects of estradiol.
• Testosterone is a male hormone, typically delivered by injection and patch, used for men with hypogonadism due to LH or GH deficiency.
• Human growth hormone (HGH) is a synthetic form of GH, delivered by injection, that is used to treat a diagnosed GH deficiency or hypogonadism.
• Desmopressin, a manmade form of ADH available as a tablet or nose spray, is used in people with excessive urination due to an ADH deficiency.
• Human chorionic gonadotrophin (HCG) is a hormonal often prescribed as an injection (often in tandem with FSH) to stimulate ovulation in women with impaired fertility due to an LH deficiency.
• Levothyroxine is a synthetic thyroid drug used to treat hypothyroidism (low thyroid function) caused by a TSH deficiency.

Periodic blood tests will likely be needed to track your hormone levels and adjust treatment as needed. You may also need occasional CT or MRI scans to monitor a pituitary condition.

Surgery is uncommonly used to treat hypopituitarism unless there a tumor or growth that can reasonably be removed without harm. Instead, high-dose radiation may be used to shrink or control the tumor. If cancer is involved, chemotherapy may be prescribed.

A Word From Verywell

Hypopituitarism is an uncommon disorder that may be hard to recognize at first because the symptoms are often so non-specific. Even if a hormone deficiency is confirmed, it may take time the underlying cause is identified. In such cases, you will likely be referred to an endocrinologist who specializes in the diagnosis, treatment, and management of hormonal disorders.

To find one near you, you can either ask your healthcare provider for a referral or use the online locator offered by the American Association of Clinical Endocrinologists.