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• Pituitary gland (hypophysis)


  • Lies in the sella turcica
  • Connected to the hypothalamus by the pituitary stalk
  • Two distinct portions: anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)
• Anterior pituitary (adenohypophysis)


  Originates from the Rathke's pouch, pharyngeal epithelium
• Posterior pituitary (neurohypophysis)


  Originates from a neural tissue outgrowth from the hypothalamus
• Pars intermedia


  • Between the anterior and posterior pituitary
  • Less developed in humans, not is animals
• Hormones of the anterior pituitary (GATFL)


  • Growth hormone
  • Adrenocorticotropic hormone (corticotropin)
  • Thyroid-stimulating hormone (thyrotropin)
  • Prolactin
  • Follicle-stimulating hormone and luteinizing hormone
• Growth hormone


  • Promotes growth of the entire body by affecting protein formation, cell replication and cell differentiation
• Adrenocorticotropic hormone (corticotropin)


  • Controls the secretion of some of the adrenocortical hormones, which affects metabolism of glucose, proteins and fats
• Thyroid-stimulating hormone (thyrotropin)


  • Controls the secretion rate of thyroxine and triiodothyronine which control the rates of most intracellular chemical reactions in the body
• Prolactin


  • Promotes mammary gland development and milk production
• Follicle-stimulating hormone and luteinizing hormone


  • Control growth of ovaries and testes as well as their hormonal and reproductive activities
• Hormones of the posterior pituitary

  • Antidiuretic hormone (vasopressin)
  • Oxytocin
• Antidiuretic hormone (vasopressin)


  • Controls the rate of water excretion into the urine
  • Control water concentration in the body fluids
• Oxytocin


  • Helps express milk from the glands of the breast to the nipples during suckling
  • Helps in delivery of the baby at the end of gestation
• The Anterior Pituitary Gland Contains Several Different Cell Types that Synthesize and Secrete Hormones
• Five cell types of the anterior pituitary gland

  • Somatotropes
  • Corticotropes
  • Gonadotropes
  • Thyrotropes
  • Lactotropes
• Somatotropes


  • Secrete human growth hormone (hGH)
  • 30% to 40% of anterior pituitary cells
• Corticotropes


  Secrete adrenocorticotropic hormone (ACTH)
• Gonadotropes


  Secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
• Thyrotropes


  Secrete thyroid-stimulating hormone (TSH)
• Lactotropes


  Secrete prolactin (PRL)
• Posterior Pituitary Hormones are Synthesized by Cell Bodies in the Hypothalamus
• Magnocellular neurons


  • Secrete posterior pituitary hormones
  • Located in the supraoptic and paraventricular nuclei of the hypothalamus
• Secretion of hormones from the posterior pituitary

  Controlled by nerve signals that originate in the hypothalamus and terminate in the posterior pituitary
• Secretion of hormones by the anterior pituitary

  • Controlled by hormones called hypothalamic releasing and hypothalamic inhibitory hormones secreted by the hypothalamus
  • These hormones are conducted to the anterior pituitary through the hypothalamic-hypophysial portal vessels
• Median eminence


  • Lowest most portion of the hypothalamus
  • Connects inferiorly with the pituitary stalk
  • Functional link between hypothalamus and the anterior pituitary gland
• Hypothalamic Releasing and Inhibitory Hormones


  • Secreted in the median eminence
  • Carried to the sinuses of the anterior pituitary via the hypothalamic-hypophysial portal system
• Hypothalamic Releasing and Inhibitory Hormones that Control Anterior Pituitary Secretion

  • Thyrotropin-releasing hormone
  • Corticotropin-releasing hormone
  • Growth hormone-releasing hormone
  • GHIH (somatostatin)
  • Gonadotropin-releasing hormone
  • Prolactin inhibitory hormone (dopamine)
• Thyrotropin-releasing hormone


  • Causes release of TSH (Thyroid Stimulating Hormone)
• Corticotropin-releasing hormone


  • Causes release of ACTH
• Growth hormone-releasing hormone


  • Causes release of GH
• GHIH (somatostatin)


  • Inhibits the release of GH
• Gonadotropin-releasing hormone


  • Causes the release of LH and FSH
• Prolactin inhibitory hormone (dopamine)

  • Causes inhibition of prolactin secretion
• All or most of the hypothalamic hormones are secreted at nerve endings in the median eminence before transported to the anterior pituitary gland
• Growth hormone (somatotropin)


  • Protein molecule
  • Contains 191 amino acids in a single chain
  • Causes growth of almost all tissues in the body
• Once the epiphyses of the long bones have united, further lengthening cannot occur
• Growth Hormone


  • Increased rate of protein synthesis in most cells the body
  • Increased mobilization of fatty acids from adipose tissue
  • Decreased rate of glucose utilization throughout the body
• Growth hormone


  • Promotes protein deposition in tissues
  • Enhance amino acid transport through the cell membrane
  • Enhance RNA translation to cause Protein synthesis by the ribosomes
  • Increase nuclear transcription of DNA to form RNA
  • Decrease catabolism of protein and amino acids
• Factors That Stimulate Secretion of Growth Hormone

  • Decreased blood glucose
  • Decreased blood free fatty acid levels
  • Increased blood amino acid levels (arginine)
  • Starvation or fasting, protein deficiency
  • Trauma, stress, excitement
  • Exercise
  • Testosterone, estrogen
  • Deep sleep (stages 2 and 4)
  • Growth hormone-releasing hormone
  • Ghrelin
• Factors That Inhibit Secretion of Growth Hormone

  • Increased blood glucose level
  • Increased blood free fatty acid levels
  • Aging
  • Obesity
  • Growth hormone Inhibitory hormone (somatostatin)
  • Growth hormone (exogenous)
  • Insulin-like growth factors (somatomedins)