Hypopituitarism - A Detailed Description

Introduction:

The pituitary gland is the master endocrine gland; therefore, any problem associated with the gland causes an overall effect on the whole body. Hypopituitarism is the inability of the gland to produce and secrete one or more of its hormones. Hypopituitarism can be primary or secondary depending upon its cause, and it is a rare and severe endocrine disease. The condition may progress slowly and remain asymptomatic for a long time. Although a slow-progressing partial hormone deficiency may go unnoticed for years, a sudden and complete lack of hormone secretion is a medical emergency that necessitates emergency medical intervention. The symptoms of hypopituitarism depend on the condition's cause, affected hormones, and the age of onset of the disease.

What Is a Pituitary Gland?

The pituitary gland, which is about the size of a pea and is positioned near the base of the brain, is an essential endocrine gland. The pituitary gland weighs about 0.5 grams and measures about half an inch in diameter in humans. The size of the pituitary gland differs between males and females. The pituitary gland doubles in size during pregnancy. Because it regulates the operation of multiple other endocrine glands, the pituitary gland is often known as the "master gland." The pituitary gland, for example, is connected to the hypothalamus by a stalk of neurons and blood vessels. The pituitary gland is responsible for various vital body functions. The pituitary gland is divided into two lobes, which contain different types of cells that produce various kinds of hormones. The lobes of the pituitary gland are:

• Anterior lobe.

• Posterior lobe.

What Are Pituitary Hormones and Their Functions?

Several hormones (signaling molecules) produced by the anterior and posterior lobes of the pituitary gland responsible for controlling other endocrine glands and various other vital functions are known as pituitary hormones. Pituitary hormones and their functions are:

Anterior Lobe:

• Human growth hormone (GH) regulates growth and development, especially in muscles and bones.

• Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce and secrete thyroid hormones.

• Adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce cortisol and other hormones.

• Follicle-stimulating hormone (FSH) regulates menstrual cycles and the growth of eggs' in women's ovaries. And helps in sperm production in men.

• Luteinizing hormone (LH) is involved in estrogen and testosterone production in women and men.

• Prolactin is involved in milk production in the mammary glands in women after childbirth.

• Endorphins regulate pain and are also involved in pleasure centers in the brain.

• Enkephalins are associated with endorphins and have similar functions.

Posterior Lobe:

• Vasopressin - Also known as the antidiuretic hormone, is responsible for water retention and maintaining a fluid-electrolyte balance in the body.

• Oxytocin - This hormone causes the smooth muscles of the uterus to contract during labor and the contraction of breast muscles to produce milk.

What Is Hypopituitarism?

• Hypopituitarism means an underactive pituitary gland, and the condition is characterized by failure of the pituitary gland to produce one or more of the pituitary hormones. It is a rare and chronic endocrine disorder affecting one or both the lobes of the pituitary gland.

• Selective hypopituitarism is a disorder in which the release of one specific pituitary hormone is reduced.

• The term panhypopituitarism refers to a decrease in the secretion of most or all of the pituitary hormones.

• Hypopituitarism manifests itself in various ways, depending on which hormones are under-secreted, the age of onset, speed, and degree of loss of hormones, and the underlying cause of the problem.

• Based on their cause, hypopituitarism has two types; primary and secondary.

What Are the Other Names of Hypopituitarism?

Alternative names of hypopituitarism are:

• Panhypopituitarism.

• Pituitary insufficiency.

What Causes Hypopituitarism?

Primary hypopituitarism occurs due to disorders of the pituitary gland, and it is caused by the loss or dysfunction of pituitary hormone-secreting cells (thyrotropes, lactotrophs, corticotrophs, somatotropes, and gonadotropes). On the other hand, secondary hypopituitarism is caused by disorders of the hypothalamus or pituitary stalk that disrupt the nerve or vascular connections to the pituitary gland, resulting in reduced pituitary hormone secretion. Various causes of hypopituitarism include:

• Pituitary neoplasms or pituitary tumors (adenomas, craniopharyngiomas, meningiomas, kidney cell cancer, breast cancer, etc.)

• Ischemic necrosis of the pituitary gland occurs due to excessive blood loss and hypovolemic shock. These conditions include diabetes mellitus and post-partum blood loss (Sheehan's syndrome).

• Systemic diseases like sickle cell anemia, eclampsia (seizures that occur during pregnancy or shortly after giving birth), inflammation of blood vessels in the temporal region of the skull (temporal arteritis), atherosclerosis (fat and cholesterol build-up in the walls of the artery), etc.

• Pituitary apoplexy (commonly caused by bleeding inside a noncancerous tumor of the pituitary gland).

• Thrombosis (formation of blood clots) in the cavernous sinus.

• Infectious diseases like tuberculosis, malaria, HIV, fungal diseases, etc.

• Head injuries.

• Brain surgery.

• Radiation therapy of the head and neck.

• Stroke (Interruption of the brain's blood flow causes damage).

• Hypophysitis (pituitary gland inflammation occurs due to the body's autoimmune response).

• In rare cases, hypopituitarism may occur due to genetic mutation. The ability of the pituitary gland to produce one or more of its hormones is affected by these mutations, which frequently begin at birth or in early childhood.

• Hypopituitarism can also be caused by tumors or illnesses of the hypothalamus, a part of the brain located directly above the pituitary gland.

• In rare cases, the cause of hypopituitarism is unknown.

• Certain drugs can also cause hypopituitarism.

Is Hypopituitarism a Common Condition?

• Hypopituitarism is a rare condition with a prevalence rate of 300 to 455 per million people.

• The actual number of cases may be underestimated, although roughly 30 % to 70 % of individuals with brain damage have signs of reduced pituitary gland hormone secretion.

• Hypopituitarism can occur in 10 % to 25 % of the cases after surgery to remove a pituitary tumor.

What Are the Symptoms of Hypopituitarism?

The signs and symptoms of hypopituitarism depend on the affected hormone, age of onset, degree of hormone loss, and the underlying cause of hypopituitarism.

Symptoms of hypopituitarism due to growth hormone deficiency:

• In children, growth hormone deficiency causes short stature and reduced overall growth.

• In adults, growth hormone deficiency may not cause any symptoms.

• Fatigue.

• Weakness of muscles.

• Change in fat composition in the body.

• Depression.

• Social anxiety.

Symptoms of hypopituitarism due to luteinizing hormone and follicle-stimulating hormone are:

• The deficiency of these hormones affects the reproductive functioning in women and men.

• Symptoms in women include; irregular menstrual cycles, infertility, low sex drive, hot flashes, loss of genital hair, inability to produce milk during lactation, etc.

• Symptoms in men include; low sex drive, erectile dysfunction, altered mood, reduced facial and body hair, etc.

• Growth hormone deficiency in adolescents causes delayed puberty.

Symptoms of hypopituitarism due to thyroid-stimulating hormone deficiency:

• Weakness.

• Unusual weight gain.

• Dryness of skin.

• Constipation.

• Sensitivity to hot and cold.

Symptoms of hypopituitarism due to adrenocorticotropic hormone deficiency include:

• Weakness and fatigue.

• Hypotension (low blood pressure).

• Fainting.

• Increased susceptibility to infections.

• Nausea and vomiting.

• Pain in the abdomens.

• Confusion and absent-mindedness.

Symptoms of hypopituitarism due to antidiuretic hormone deficiency are:

• Frequent urination.

• Excessive thirst.

• Electrolyte imbalance.

Symptoms of hypopituitarism due to prolactin deficiency:

• A problem in milk formation during lactation or after childbirth.

How Is Hypopituitarism Diagnosed?

The diagnosis of hypopituitarism is made in the following ways:

• Blood Examinations: The levels of several hormones produced by the pituitary gland are checked. The levels of the hormones produced by the peripheral endocrine glands are also checked because these glands are controlled by the pituitary hormones. Hypopituitarism is diagnosed by assessing basal hormone levels in the morning fasting state or, if necessary, by performing stimulation tests. The distinction between hypopituitarism and primary target organ hormone deficit can be made easily by measuring basal hormone levels. If there is an increase in pituitary hormone levels but a target organ hormone deficiency, the differentiation of a target organ deficiency from a pituitary gland disease becomes easy, but a stimulation test may be required to establish the cause of the condition.

• Imaging Tests: A brain CT scan (computed tomography) or MRI (magnetic resonance imaging) may be done to check for the presence of pituitary tumors, adenomas, etc. These imaging tests are also helpful in determining the growth, size, and extent of pituitary tumors.

• Vision Tests: Testing the vision or the eye sigt is important because, in the case of pituitary tumors, a large growth can cause compression of the surrounding nerves (especially the optic chiasma), which may lead to visual field defects.

How Is Hypopituitarism Treated?

The first line of treatment while managing hypopituitarism includes medications or hormone replacement therapy to restore the normal pituitary hormone levels in the body. Medications include:

• Corticosteroids: A lack of the adrenocorticotropic hormone, and subsequent cortisol deficiency, is treated by supplementing with steroid pills such as Hydrocortisone or Prednisolone, which are given by mouth in doses twice or three times a day.

• Levothyroxine: Thyroid-stimulating hormone deficiency can result in low thyroid hormone (thyroxine and triiodothyronine) levels, which can be treated with Levothyroxine or L-thyroxine.

• Sex Hormones Replacement Therapy: This includes the administration of testosterone in men and a combination of estrogen and progesterone in women. Testosterone is given as an injection or a patch or gel applied to the skin. Pills, gels, and patches are also available for female hormone replacement.

• Growth Hormone: Somatropin, Genotropin, Humatrope, etc., are given to replace the growth hormone. These are delivered using a needle inserted beneath the skin. It encourages growth, which aids in developing a more average height in children. Adults with growth hormone deficiency symptoms may benefit from growth hormone replacement, but they will not grow taller.

• Fertility Hormones: Gonadotropins are given to women to stimulate ovulation. In men, it helps in sperm production.

• Desmopressin: It is a drug that can be given as a nasal spray, pill, or injection and is used to replace the antidiuretic hormone.

Surgery may be required in the case of pituitary tumors to control the growth and provide relief from compressive symptoms.

Conclusion:

Hypopituitarism is rare but can progress to become a medical emergency in certain patients. The treatment involves taking life-long hormone replacement therapy. After effective treatment, complete or partial recovery of the body's ability to produce pituitary hormones may be attainable. Therefore, the prognosis of hypopituitarism is good.