What Is Acquired Hypopituitarism?
The pituitary gland is an organ present at the base of the brain that produces growth and sexual development hormones. The pituitary gland produces hormones that help to carry out various bodily functions like growth metabolism, energy production from food, and reproduction. These hormones are directly released in the blood flow. Hypopituitarism is a disorder characterized by the failure of the pituitary gland to produce one or more hormones or not producing enough hormones to carry out bodily functions. It refers to complete or partial loss of anterior or posterior pituitary hormone secretion. It can develop as a result of individual anterior pituitary cell types or hypothalamic function, acquired disease of the pituitary or hypothalamus, or infundibulum lesions that interfere with the hypothalamic control of the pituitary.
Congenital hypopituitarism is the condition present by birth, whereas acquired hypopituitarism can be observed later in life due to several neurological diseases. Acquired hypopituitarism occurs as a result of hypothalamic or pituitary tumors, any damage to the hypothalamus, pituitary stock, or anterior pituitary. The symptoms, diagnosis, and treatment depend upon the low hormone.
What Are the Causes of Acquired Hypopituitarism?
1. Neoplasms:
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Pituitary Adenoma - Pituitary adenomas can be non-functioning or can secret one or more anterior pituitary hormones. Their classification is made depending upon the size and presence of extrasellar extension. A pituitary adenoma is a low-grade-secreting tumor and does not cause clinically recognized symptomatology.
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Craniopharyngioma - Craniopharyngioma is a benign neoplastic lesion that originates from embryological remnants of Rathke's pouch. These are a type of intracranial tumors and generally have a better prognosis in adults.
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Rathke's Cysts - Rathke's cysts are epithelial cysts that originate from remnants of Rathke's pouch. The symptoms include amenorrhea or galactorrhea, causing visual disturbances and headaches.
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Peri-pituitary Tumor - It is a type of meningioma with well-circumscribed masses originating from the sphenoid ridge. Metastasis to the pituitary gland can be present as interstellar masses resulting in hypopituitarism, diabetes insipidus, or pressure effects.
2. Immunological or Inflammatory Diseases:
Lymphocytic hypophysitis is a pituitary mass lesion with partial hypopituitarism, mainly occurring in pregnancy. It is a rare condition in which the pituitary gland becomes attacked by the lymphocytes. Lymphocytes are the cells responsible for immunity. This results in enlargement and malfunction of the pituitary gland. Sarcoidosis affects multiple systems in the body and is characterized by the presence of non-caseating granulomatous.
3. Infections:
Bacterial infections from sinus or meningeal sepsis can affect the pituitary gland to form an abscess. Pituitary tuberculomas can occur in the context of generalized tuberculous disorder with meningitis. Fungal infections of the pituitary gland can occur as a complication of AIDS (acquired immunodeficiency syndrome), and hypopituitarism with pituitary necrosis can be seen in toxoplasmosis
4. Radiation Therapy:
Hypopituitarism is a common complication of radiation therapy after pituitary adenomas, head and neck tumors, cranial irradiation for acute lymphoblastic leukemia, or intracranial malignancy.
5. Traumatic Brain Injury:
Hypopituitarism is generally associated with traumatic brain injury and endocrine dysfunction. Multiple pituitary deficiencies or isolated pituitary deficiencies are rare.
What Are the Symptoms of Acquired Hypopituitarism?
The pituitary gland secretes various hormones, and their deficiency can cause different signs and symptoms in the body. They are enumerated as follows -
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Adrenocorticotropic Hormone - Weakness, fatigue, dizziness, nausea, vomiting, circulatory failure, Addison’s disease, and absence of hyperkalemia.
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Thyroid-Stimulating Hormone - Growth retardation in children, fatigue, cold intolerance, constipation, weight gain, slow relaxing reflexes, and dry skin in adults.
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Gonadotropins - Delayed puberty in children and impaired fertility, reduced libido, decreased muscle mass, decreased bone mass, decreased hair growth, fine wrinkles, and testicular hypertrophy in adults.
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Growth Hormone - Growth retardation, increased adiposity, and short stature in children. In adults, reduced exercise capacity, increased cardiovascular risk, increased central obesity, reduced lean body mass, and impaired psychological well-being.
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Antidiuretic Hormone - Polyuria and polydipsia.
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Prolactin Hormone - Failure of breast milk production after giving birth.
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Oxytocin Hormone - Breast milk flow issues after childbirth, lack of empathy, and difficulty interacting with others.
How to Diagnose Acquired Hypopituitarism?
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Magnetic Resonance Imaging (MRI) - MRI scans can be used to detect the presence of tumors and their location in the brain.
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Computed Tomography (CT) - A brain CT scan provides the result for the presence of pituitary adenoma or any other non-cancerous tumor that can cause hyperpituitarism.
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Baseline Investigations of Pituitary Function - Gonadal axis for testosterone, albumin, LH, FSH for men and oestradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone for women. Prolactin, insulin-like growth factor-1, growth hormone, paired plasma, and urine osmolality, thyroid axis for free helper T cells with CD4 molecule (T4) and thyroid-stimulating hormone (TSH), and adrenocortical axis for serum cortisol.
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Dynamic Testing - A stimulation test is done when hypofunction is suspected. These tests are designed to assess the reserve capacity to form and secrete a hormone. Dynamic pituitary function tests assess the hypothalamic-pituitary unit or directly stimulate the anterior pituitary with pharmacological doses of synthetic hypothalamic peptides, and the pituitary hormone response is measured.
What Are the Risk Factors Associated With Acquired Hypopituitarism?
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Radiation Therapy or a History of Cancer - The treatment of cancer can involve radiation therapy which poses a risk for the development of hypopituitarism.
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Head or Brain Trauma - Most cases of acquired hypopituitarism result after a brain or head injury.
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Sickle Cell Anemia - It is a type of anemia that can cause a deficiency of pituitary hormones.
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Type 1 Diabetes Mellitus - Poorly managed diabetes mellitus can develop complications like nerve and vascular damage and contribute to hyperpituitarism.
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Genetic Mutations - Mutations in the genes can also cause hypopituitarism.
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Pregnancy - Pregnant women are at higher risk of developing lymphocytic hypophysitis. Severe blood loss after childbirth can result in acquired hypopituitarism. This is called Sheehan syndrome.
How Is Acquired Hypopituitarism Treated?
The treatment for acquired hypopituitarism depends on the cause. The treatment modality can include the following- -
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Hormone Replacement Therapy - This therapy aims to restore deficient pituitary hormones to their normal levels.
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Surgery - Tumors or trauma causing hypopituitarism can be treated using surgery.
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Radiation Therapy - Some tumors can require radiation in order to check their spread.
Conclusion :
Acquired hypopituitarism can occur in any age of life. There are various reasons causing hypopituitarism, which results in a deficiency of pituitary hormones in the body. A history of cancer or radiation therapy, head or brain trauma, sickle cell anemia, diabetes, genetic mutations, and pregnancy can act as factors for hyperpituitarism. The prognosis depends on the cause and the age of onset, the level of lacking the affected hormone, and the response of the body to the treatment. Although hypopituitarism is a rare phenomenon, it can result in a medical emergency.
