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The Anterior Lobe of the Pituitary is glandular tissue and a part of the endocrine system. The release of its trophic (meaning "tending to change") hormonal secretions is under the control of the hypothalamus. It is the altering effects of the anterior pituitary's trophic hormones, in particular, that qualify the pituitary as "master gland".
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The formal anatomical name for the anterior pituitary is "adenohypophysis", named so because of its endocrine or glandular role (Parent, 1996).
Complications during childbirth that result in the hemorrhaging or excessive bleeding of the uterus are associated with anterior pituitary dysfunction. In this condition, called Sheehan's syndrome, the blood supply to the anterior pituitary is disrupted resulting in neuronal death and hypopituitarism (Huan, Ting, Hsu & Tsai, 2000). The pituitary gland is particularly sensitive to the disruption of blood flow because it is enlarged during pregnancy and has a greater need for oxygen. Because the posterior pituitary is rarely affected by the disruption of blood flow, the symptoms associated with Sheehan's syndrome are associated with a selective reduction of anterior pituitary function. Thus, a reduction in TSH, prolactin, ACTH, FSH, and LH results. The first clinical sign of Sheehan's syndrome is a loss of lactation following childbirth.
Recently discovered cells in the anterior pituitary, called folliculo-stellate cells (Inoue et.al., 1999), do not produce hormones, but a variety of cytokines (Turnball & River, 1999) or growth factors (such as fibroblast growth factor). These growth factors increase the proliferation and differentiation of pituitary cells, and appear to underlie normal pituitary cell turnover and possibly the formation of pituitary tumors (Arzt, 1999). Because a better understanding of the folliculo-stellate cells may lead to improved treatment of pituitary dysfunction and tumors, they are receiving much attention in the laboratory.
| References |
Arzt, E., Pereda, M.P., Castro, C.P., Pagotto, U., Renner, U., Stalla, G.K. (1999). Pathophysiological role of the cytokine network in the anterior pituitary gland. Frontiers in Neuroendocrinology, 21(1), 71-95.
Huan, Y.Y., Ting, M.K., Hsu, B.R. & Tsai, J.S. (2000). Demonstration of reserved anterior pituitary function among patients with amenorrhea after postpartum hemorrhage. Gynecological Endocrinology, 14(2), 99-104.
Inoue, K., Couch, E.F., Takano, K., Ogawa, S. (1999). The structure and function of folliculo-stellate cells in the anterior pituitary gland. Archives of Histology and Cytology, 62(3), 205-218.
Parent, A. (1996). Carpenter's human neuroanatomy (9th ed.). London: Williams & Wilkins.
Turnball, A.V., Rivier, C.L. (1999). Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiological Review, 79(1), 1-71.