Hypopituitarism

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Hypopituitarism is a medical term describing the deficiency (hypo) of one or more hormones of the pituitary gland. The hypothalamus regulates pituitary secretion by the production of releasing hormones and posterior pituitary hormones and hence its dysfunction can also lead to hypopituitarism.

In endocrinology, deficiency of one or multiple hormones of the anterior pituitary is generally referred to as hypopituitarism, while deficiency of the posterior lobe generally only leads to central diabetes insipidus. The deficiency of all anterior pituitary hormones is termed panhypopituitarism.

Pathophysiology

• The hormones of the anterior pituitary include 2 proteins, 3 glycoproteins and a polypeptide:

1. prolactin (PRL) - stimulates milk production in the breast
2. growth hormone (GH) - growth and glucose homeostasis
3. luteinizing hormone (LH) - menstrual cycle and reproduction
4. follicle stimulating hormone (FSH) - same
5. thyroid stimulating hormone (TSH) - stimulates thyroxine production in the thyroid
6. adrenocorticotropic hormone (ACTH) - stimulates glucocorticoid production in the adrenal gland

• These hormones excreted are secreted in individually characteristic pulsatile patterns, often with distinct circadian rhythm, rather than at steady rates throughout 24 hours.
• The posterior pituitary is the site of release of the nonapeptide hormones antidiuretic hormone (ADH) and oxytocin, the former regulating plasma osmolarity and the latter regulating uterine contractions during childbirth as well milk ejection from the breasts.
• Deficiency of a single pituitary hormone occurs less commonly than deficiency of more than one hormone. Sometimes referred to as progressive pituitary hormone deficiency or partial hypopituitarism, there is usually a predictable order of hormone loss.
• Generally, growth hormone is lost first, then luteinizing hormone deficiency follows. The loss of follicle-stimulating hormone, thyroid stimulating hormone, adrenocorticotopic hormones and prolactin typically follow much later. The progressive loss of pituitary hormone secretion is usually a slow process, which can occur over a period of months or years. Hypopituitarism does occasionally start suddenly with rapid onset of symptoms
• Most people with hypopituitarism lack growth hormone as well as one or more others. As for the posterior pituitary, antidiuretic hormone deficiency is the main problem, while oxytocin deficiency rarely causes clinically significant problems.

Causes

Common Causes

Hypopituitarism and panhypopituitarism can be congenital or acquired. A partial list of causes and forms:

• Congenital hypopituitarism
  • Hypoplasia of the pituitary
    • Isolated idiopathic congenital hypopituitarism
    • Associated with other congenital syndromes and birth defects
      • Septo-optic dysplasia
      • Holoprosencephaly
      • Chromosome 22 deletion syndrome
      • Rapaport syndrome
  • Single gene defect forms of anterior pituitary hormone deficiency
• Acquired hypopituitarism (Simmonds' disease)
  • trauma (e.g., skull base fracture)
  • surgery (e.g., removal of pituitary neoplasm)
  • tumor - secretory and non-secretory (20%) pituitary or hypothalamic neoplasms, cause hypopituitarism by compressing the remaining tissue
  • inflammation (e.g. sarcoidosis or autoimmune hypophysitis)
  • radiation (e.g., after cranial irradiation for childhood leukemia)
  • shock
    • (Sheehan's syndrome is hypopituitarism after heavy bleeding in childbirth)
  • hemochromatosis
• other diseases.

Causes in Alphabetical Order

• Anorexia Nervosa
• Bulimia Nervosa
• Changes in body weight
• Congestive Heart Failure
• Emotional disorders
• Empty Sella Syndrome
• Habitual exercise
• Head Trauma
• Hemochromatosis
• Infection

• Fungal
• Malaria
• Meningitis
• Syphillis
• Tuberculosis

• Ischemic nerosis of the pituitary

• Anticoagulant therapy
• Arteriosclerosis
• Arteritis temporalis
• Blood dyscrasias
• Brain Trauma
• Diabetes Mellitus
• Eclampsia
• Increased cranial pressure
• Sheehan's Syndrome
• Sickle Cell Anemia
• Tumor

• Iatrogenic
• Parasellar tumor/pituitary compression

• Craniopharyngioma
• Chromophobe adenoma
• Intracranial cartoid branch aneurysm
• Lymphoma
• Meningioma
• Metasteses
• Optic nerve neurinoma

• Pituitary adenomas
• Renal Failure
• Sarcoidosis
• Wegener's Granulomatosis

Diagnosis

Symptoms

Hypopituitarism may come to medical attention by symptoms or features of pituitary hormone deficiency

• poor growth
• Micropenis
• Polyuria
• Impaired libido
• fatigue
• Muscle weakness
• Weight loss
• Headache
• Nausea and vomiting
• Loss of appetite
• Diarrhea

Physical Examination

Vital Signs

• Hypotension

Genitals

• Micropenis

Laboratory Findings

Electrolyte and Biomarker Studies

• ACTH stimulation test: The ACTH stimulation test is the most common test for patients who are suspected of diagnosing adrenal insufficiency. During this test, before and after being injected ACTH, the patient is detected with the level of blood cortisol and urine cortisol. In normal person, after an ACTH injection, it may show a rise in blood and urine cortisol levels. Patients with causes of adrenal insufficiency have little or no increase in cortisol levels.
• CRH stimulation test: This test can differ the primary and secondary adrenal insufficiency. In this test, the patient is injected synthetic CRH and measured blood cortisol before and 30, 60, 90, and 120 minutes after the injection. The leval of blood cortisol in people with primary adrenal insufficiency such as Addison’s disease, demonatrates high levels of ACTH but no cortisol. For the patients with secondary adrenal insufficiency, they appear absent or delayed ACTH.
• A provocative test (triple bolus test) measures the secretory response of the pituitary to a stimulus (other hormones, drugs, exercise, etc.) by measuring serum levels of the hormone involved.

X Ray

• Abdominal x-ray test: An x-ray image of abdominen allows the doctor to check the shape and size of the adrenal glands.

CT

• These imaging tests can confirm the size and shape of pituitary gland and hypothalamus and show the organs near them. It is useful for the diagnosis of secondary adrenal insufficiency. CT scan produce a series of x-ray pictures giving cross-sectional images.

MRI

• A magnetic resonance imaging (MRI) scan may show a three-dimensional image of this region.

Ultrasound

• Abdominal ultrasound: This is an painless test which uses sound waves to create a picture of the internal organs. It can help doctor reveal any signs in adrenal glands.

Treatment

Hypopituitarism and panhypopituitarism are treated by replacement of appropriate hormones. Since most of the anterior pituitary hormones are proteins or glycoproteins released in pulsatile patterns, whose functions are to induce secretion of smaller molecule hormones (thyroid hormones and steroids), it is simpler and less expensive for most purposes to simply replace the target gland hormones. There are a few exceptions, such as fertility induction.

• GH is replaced with growth hormone.
• TSH is replaced with thyroxine.
• ACTH is usually replaced with hydrocortisone but any glucocorticoid may be used.
• LH and FSH are most often replaced by supplying the appropriate sex steroids (e.g., testosterone or estrogen and progestin). Virtually all people who need T or E2 replacement for hypopituitarism rarely have spontaneous, effective spermatogenesis or follicular maturation. Both GnRH by subcutaneous pump and gonadotropins (Pergonal) by daily subcutaneous injections have been used effectively to induce fertility.
• Prolactin is not usually replaced, as infant formula is readily available, simpler, and much cheaper.
• ADH is replaced most commonly with oral, nasal, and sometimes intravenous or subcutaneous desmopressin.
• Oxytocin is most important during labor and delivery at the end of pregnancy, and can be replaced in that circumstance by pitressin.

See also

• growth hormone deficiency
• pituitary gland
• Kallmann syndrome
• Empty sella syndrome
• Insulin tolerance test

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