Hypopituitarism

The pituitary gland, often referred to as the master gland, controls the function of multiple endocrine glands. It can be damaged by trauma, internal insult (loss of blood flow), and external insult such as radiation therapy. Hypopituitarism is defined as either partial or complete deficiency of anterior or posterior pituitary hormone secretion. Hormones secreted by the pituitary gland include growth hormone (GH); thyroid stimulating hormone (TSH); the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH); prolactin (PRL); adrenocorticotropic hormone (ACTH); oxytocin; and vasopressin (antidiuretic hormone). Evaluation of pituitary function and determination of the site of pathology often require testing of hormones released as well as end products.

Quick Answers for Clinicians

Diagnosis

Indications for Testing

  • Anterior pituitary – symptoms compatible with multiple pituitary hormone deficiencies
    • Fatigue, depression, and other endocrine disorders
  • Posterior pituitary – symptoms of central diabetes insipidus
    • Polydipsia, polyuria, and nocturia
    • Children – fever, weight loss, irritability, delayed growth
  • Incidental pituitary lesion noted on imaging

Laboratory Testing

  • Anterior pituitary testing
  • Posterior pituitary testing (vasopressin/antidiuretic hormone testing)
    • Urine osmolality (UO) and/or serum/plasma osmolality (SO) and serum/plasma sodium (Na)
      • UO<SO and high Na – central diabetes insipidus
      • UO<250 mOsm/kg and low Na – primary polydipsia
      • UO<SO and normal Na – perform water deprivation test in hospital and order SO
        • SO>290 mOsm/kg, Na>140 mmol/L, and weight loss nearing 3% – diabetes insipidus
          • Order antidiuretic hormone (ADH)/arginine vasopressin hormone (AVH) plasma
            • High ADH/AVH– nephrogenic diabetes insipidus
            • Low ADH/AVH – central diabetes insipidus
          • Alternatively, administer vasopressin and order UO 1-2 hours post administration
            • >50% increased UO – central diabetes insipidus
            • <50% increased UO – nephrogenic diabetes insipidus

Histology

  • If pituitary adenoma is present, immunohistochemistry and pathologist examination may be required
  • Consider prolactin, growth hormone, or ACTH
  • For detailed descriptions, refer to ARUP’s Immunohistochemistry Stain Offerings

Imaging Studies

Magnetic resonance imaging (MRI) brain scan is the imaging of choice for pituitary masses.

Background

Epidemiology

  • Incidence  – 4-5/100,000
  • Age – incidence increases with age

Etiology

Pathophysiology

  • Anterior pituitary produces 6 major hormones
  • Posterior pituitary produces 2 major hormones
    • Oxytocin
    • Antidiuretic hormone/arginine vasopressin hormone (ADH/AVH)
  • Any insult to gland or vascular supply may cause hormone deficiency (hypopituitarism)
    • Loss of any of these hormones produces symptoms based on the hormones lost

Clinical Presentation

  • Varied – dependent on the region of pituitary gland involved and age of patient
  • Nonspecific
    • Headache
    • Visual disturbances
    • Weakness
  • Anterior pituitary
    • Gonadotropic hormones (FSH, LH, PRL)
    • GH
      • Adults – fatigue, decreased muscle mass and strength, reduced bone marrow density
      • Children – short stature, failure to thrive
      • Infants – seizures, hypoglycemia
    • ACTH
      • Adults – fatigue, nausea, vomiting
      • Children/infants – acute adrenal crises with shock
    • TSH
      • Adults – weight gain, coarse hair, fatigue
      • Children/infants – failure to thrive
  • Posterior pituitary (hypothalamic)
    • Central diabetes insipidus
      • Adults – polydipsia, polyuria, nocturia
      • Children – vomiting, diarrhea, dry skin, weight loss, irritability
      • Infants – fever, unusually wet diapers (polyuria), delayed growth, irritability

ARUP Lab Tests

Differential diagnosis of Cushing syndrome

Screen and diagnose primary and secondary adrenal insufficiency

Aid in diagnosis of adrenal insufficiency and determining the presence of anterior pituitary tumors

Aid in diagnosis of adrenocorticotropic hormone (ACTH) deficiency in the evaluation of hypopituitarism

Assess thyroid function

Identify risk in patients with palpable thyroid nodules

Reflex: if TSH is outside the reference interval, then Free T4 testing will be added

Aid in diagnosis of gonadotropin deficiency

Aid in evaluation of suspected hypogonadism in men with a total testosterone level at the lower limit of the normal range

Not recommended for use in women and children

Suitable for measurement of estradiol in adult premenopausal women

In all other groups, the preferred test is estrogens, fractionated by tandem mass spectrometry

Recommended test for evaluating endogenous estrogen status in postmenopausal women, men, or children

Screening for anterior pituitary tumor

Aid in diagnosis of growth hormone excess or deficiency disorders

Not a first-line test in the evaluation of growth disorders

Aid in workup of suspected anterior hypopituitarism

Aid in histologic diagnosis of pituitary tumors

Stained and returned to client pathologist; consultation available if needed

Related Tests

Preferred test for screening and monitoring of thyroid function

Not the preferred initial thyroid disorder screening test

Order following an abnormal thyroid stimulating hormone (TSH) result to diagnose thyroid disease

Order in conjunction with TSH in cases of suspected secondary hypothyroidism

Aid in evaluation of suspected hypogonadism in men with a total testosterone level at the lower limit of the normal range

Not recommended for use in women and children

Screen, diagnose, and monitor diseases associated with excess or deficient cortisol production

May be useful for monitoring certain pituitary tumors

Medical Experts

Contributor

Lehman

Christopher M. Lehman, MD
Associate Professor of Clinical Pathology, University of Utah
Medical Director, University of Utah Health Hospital Clinical Laboratory, ARUP Laboratories
Contributor

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®