Excess Anterior Pituitary Syndromes

  1. Excess output of anterior pituitary hormone is usually caused by hormone-producing adenomas (carcinomas, most of which are non-functional, and hypothalamic disease are rare).

  2. Microadenomas (<10 mm in diameter; 50% of pituitary tumors) are most common with ACTH-secreting tumors, because the symptoms of hyperadrenalism are relatively prominent and announce the presence of the disorder.

  3. Macroadenomas (in-situ and removed) are more common with growth hormone and gonadotropin-producing tumors because the immediate effects of excess hormone are less prominent. If they become large enough, these tumors may produce mass effects (bitemporal hemianopsia, headaches, damage to the remaining pituitary with loss of those hormones, and brain compression).

  4. Adenomas may produce a single hormone, or multiple hormones simultaneously

  5. Prolactin-producing tumors

    • The most common pituitary tumor

    • Amenorrhea-galactorrhea in women; impotence and infertility (occ. gynecomastia) in men

    • Laboratory analysis

      • Direct immunoassay, 3 specimens at least 30 min apart (because prolactin secretion is pulsatile)

      • Avoid drugs that can induced suppression prolactin secretion prior to testing (e.g., dopamine)

  6. Growth-hormone-producing tumors

    • Produce acromegaly in adults (gigantism in younger patients)

    • About one third also release prolactin

    • Laboratory analysis

      • Direct immunoassay, multiple specimens (because secretion is pulsatile)

      • Immunoassay of Insulin-like Growth Factor-1 (IGF-1) is used as a surrogate measure for growth hormone by some authorities because it reflects GH secretion over time.
Pituitary Hormones Hypopituitarism
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Last modified: 1/16/97; Author: J. Harrison