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Hypopituitarism

Hypopituitarism

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Hypopituitarism
Hypopituitarism occurs when one or more of the pituitary hormones is deficient.
Panhypopituitarism: All 6 anterior pituitary hormones are deficient.
Diabetes Insipidus: When the posterior pituitary is affected, ADH is the most apparent loss (i.e., patients have diabetes insipidus).
Signs and symptoms: Depend on which hormones are deficient, the extent of the deficiency, and the age of onset.
Furthermore, deficiencies tend to develop in this order: Growth hormone, Luteinizing hormone, Follicle stimulating hormone, Thyroid stimulating hormone, ACTH, then Prolactin. Of course, variations occur by etiology.
Hypopituitarism is associated with increased mortality, particularly due to cardiovascular and respiratory effects.
Diagnosis: Rule out end-organ failure (for example, is TSH deficient or is the thyroid unable to respond to it?).
    • As part of this process, we can evaluate hormone levels (or use stimulation tests for GH and ACTH), and use brain imaging to look for pituitary tumors, etc.
Treatment: Hormone replacement.
Anatomy Review
Hypothalamus and pituitary gland.
    • Hypothalamus, pituitary stalk, and the anterior and posterior pituitary lobes.
Hypophyseal portal system, which carries hypothalamic hormones to the anterior pituitary.
Primary hypopituitarism: Abnormalities in the pituitary gland that produce pituitary hormone deficiencies.
Secondary hypopituitarism: Occurs when there are issues with the hypothalamus or pituitary stalk that precipitate pituitary hormone deficiencies.
Causes of Hypopituitarism
Invasive and compressive anomalies can interfere with hormone production.
    • Pituitary Adenoma: The most common cause in this category is pituitary adenoma; we show a tumor invading the space around the gland and compressing the anterior lobe where it sits in the sella turcica.
    • Pituitary apoplexy, which is associated with adenomas, can cause infarction or hemorrhaging, which further impairs hormone production.
Pituitary apoplexy can cause headaches, nausea and vomiting, and visual disturbances; can be fatal.
    • Craniopharyngiomas are a cause of invasive and compressive hypopituitarism in children, in whom we see disturbed growth from the loss of growth hormone.
More generally, tumors can interfere with pituitary hormone production. Bear in mind that this includes CNS tumors (meningioma, chordoma, etc.) and metastatic tumors (esp. of the breast and lung).
Empty sella syndrome, which is characterized by cerebrospinal fluid leaking into the sella turcica and compressing the pituitary gland.
    • Risk factors for empty sella syndrome include female sex and hypertension.
Traumatic brain injury can damage the pituitary gland – this can be the result of falls (particularly in the elderly), car accidents, and physical violence.
Iatrogenic causes include complications of treating brain tumors, etc. with radiation therapy and/or surgery.
Sheehan's syndrome is associated with hypotension and pituitary ischemia resulting from severe postpartum hemorrhage.
    • Hypopituitarism may be evident soon after birth, or later, in the form of low blood pressure, vision deficits, the inability to lactate or menstruate, or other deficiencies.
Infiltrative, granulomatous disorders can also affect the pituitary gland.
    • Two examples include sarcoidosis (neurosarcoidosis, esp. of the pituitary stalk), and Langerhans histiocytosis (which is associated with posterior pituitary involvement and diabetes insipidus).
Infectious diseases, particularly tuberculosis meningitis, syphilis, and some fungal infections are known to interfere with pituitary functioning.
Immunologic triggers can induce hypophysitis, in which infiltration of lymphocytes and inflammation causes enlargement and malfunctioning of the pituitary gland.
    • Two examples of this:
Lymphocytic hypophysitis, aka, autoimmune hypophysitis, which most often occurs in pregnant females, and, Immune checkpoint inhibitors, such as ipilimumab, that enhance T-cell activation. Since symptoms are generally non-specific, we should monitor the hormones of patients on these treatments. Hemochromatosis, is also associated with hypopituitarism; hemochromatosis, which can be congenital, occurs when excessive GI iron absorption allows for iron overload and damage to tissues, including the pituitary.
Other genetic or congenital problems can also cause hypopituitarism.
    • Combined hormone deficiencies include mutations in POU1F1, PROP-1, HESX1, and PITX2.
    • Isolated hormonal deficiencies have also been associated with specific mutations (for example, recall that defects in the TRH receptor can lead to TSH deficiencies).
Idiopathic: In some cases, no cause can be identified, so we also include "idiopathic" as an etiological category.
Signs and Symptoms of Hormone Deficiency
For a more comprehensive look at these hormonal deficiencies, please see their separate tutorials or the flashcards linked in our notes.
Growth Hormone
    • Deficiencies in children produce slowed growth.
    • Adults may experience a vague sense of lowered well-being with lethargy and loss of interest; more specific signs include a shift in body composition with decreased muscle mass and increased fat, hyperlipidemia, insulin resistance, and cardiovascular effects including endothelial dysfunction and reduced cardiac output.
LH/FSH
    • Indicate that the effects of reduced luteinizing hormone and follicle stimulating hormone may be particularly subtle, but when the deficiency is extreme, patients can experience amenorrhea, erectile dysfunction, and infertility.
    • Kallman Syndrome is a genetic absence of GnRH receptors leading to LH/FSH deficiency – this is an example of a genetic etiology for a specific hormonal deficiency.
TSH
    • Lack of thyroid stimulating hormone produces hypothyroidism without the goiter.
    • Symptoms are usually less severe than in primary hypothyroidism, but still include cold intolerance, fatigue, weight gain, muscle/joint pain, constipation, and bradycardia.
ACTH
    • ACTH deficiency and adrenal insufficiency can cause serious problems due to loss of glucocorticoid actions, including fatigue, hypotension, increased risk of infections, and hypoglycemia.
    • These effects are usually worse when the patient experiences stress - recall that cortisol is released in response to stress, but is lacking in these patients.
    • Mineralocorticoid levels (aldosterone) are often preserved, since they are primarily maintained by the renin-angiotensin-aldosterone system.
Prolactin
    • Prolactin deficiency is most obvious when lactation is deficient.
ADH
    • Antidiuretic hormone (aka, vasopressin) can be deficient when the posterior pituitary is involved – recall that ADH deficiency causes diabetes insipidus, in which the kidneys produce large volumes of hypo-osmolar urine. Patients are hypovolemic and dehydrated.
  • For references, please see the full tutorial on Hypopituitarism.

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