Hypopituitarism

Hypopituitarism

 

 

The pituitary gland is often referred to as the master gland because it orchestrates complex functioning of multiple endocrine glands.  Hypopituitarism is defined as either partial or complete deficiency of anterior or posterior pituitary hormone secretion.

Epidemiology

  • Incidence  – 45/100,000
  • Age – incidence increases with age

Etiology

  • Tumor – adenoma, lymphoma, metastatic infiltration
  • Autoimmune disease
  • Trauma – surgery, head injury, radiation
  • Vascular event – hemorrhagic apoplexy, pregnancy-related (Sheehan syndrome), sickle cell disease
  • Infections – histoplasmosis, tuberculosis, toxoplasmosis
  • Infiltrative disease – sarcoidosis, hemochromatosis
  • Genetic disease – Kallmann syndrome, Prader-Willi syndrome, Laurence-Moore-Biedl syndrome

Pathophysiology

  • Anterior pituitary produces 6 major hormones
    • Prolactin (PRL)
    • Growth hormone (GH)
    • Adrenocorticotropic hormone (ACTH)
    • Luteinizing hormone (LH)
    • Follicle-stimulating hormone (FSH)
    • Thyroid-stimulating hormone (TSH)
  • Posterior pituitary releases oxytocin and antidiuretic hormone (ADH)
  • Any insult to gland or vascular supply may cause hypopituitarism
  • Loss of any of these hormones will produce specific symptoms based on the particular hormones lost

Clinical Presentation

  • Varied – dependent on which part of the pituitary gland is involved
  • Nonspecific
    • Headache
    • Visual disturbances
  • Anterior pituitary
    • Gonadotropic hormones – sexual dysfunction and amenorrhea
    • Growth hormone – fatigue, decreased muscle mass and strength
    • Adrenal corticotrophic hormone – fatigue, nausea, vomiting
    • Thyroid hormone – weight gain, coarse hair, fatigue
    • Nonspecific – fatigue, memory disturbances, depression
  • Posterior pituitary (hypothalamic)
    • Central diabetes insipidus – polydipsia, polyuria, nocturia

Diagnosis

  • Laboratory testing
    • Based on specific symptoms
    • PRL deficiency – basal measurement of PRL
    • GH deficiency – basal morning measurement of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3)
      • In addition, test response to insulin-induced hypoglycemia (insulin tolerance test)
    • ACTH deficiency (primary adrenal insufficiency) – basal measurement, ACTH and cortisol
      • Metyrapone testing if ACTH deficiency is consideration
        • ACTH stimulation testing if primary adrenal insufficiency is a consideration
    • Gonadotropin deficiency (LH/FSH) – basal measurement LH, FSH, estradiol (female) or testosterone (male)
    • TSH deficiency – basal thyroid function testing
      • Thyroid stimulating hormone (TSH), free T4
    • ADH deficiency –  Diabetes insipidus testing
      • Urine osmolality and serum/urine sodium, serum antidiuretic hormone (ADH)
      • May require water deprivation testing
    • Releasing hormones are not recommended for use in initial testing
  • Imaging – MRI necessary to identify sellar and parasellar masses

Treatment

  • Hormone replacement based on deficiencies

See Also