Endocrine System Anterior Pituitary Gland

Anterior Pituitary Gland

• a proper gland

• known as the adnohypothesis or anterior lobe

• produces and secretes hormones but it is under the control of the hypothalamus
  - hypothalamus secretes hormones vi the hypothalamic neurons, those hormones enter the hyperphyseal portal system travel down into the anterior pituitary and stimulate the secretion of hormones from the anterior pituitary cells

Six hormones that are secreted by the anterior pituitary

1. thyroid stimulating hormone

2. follicle stimulating hormone

3. luteinizing hormone

4. adrenacoricotropic hormone

5. growth hormone

6. prolactin

• most hormones in the body are under negative feedback control and tat prevents the hormone concentration from being too high or from being to low

Growth hormone (GH)

• secreted from the anterior lobe of the pituitary gland

• produced by somatotropic cells of the anterior lobe that:
  - stimulate most cells, but target bone (bone growth) and skeletal muscle
  - promote protein synthesis and increase blood glucose and fats for fuel to the tissues trying to grow

• involved in vertical growth, determines how tall you are

• has a permissive relationship with the thyroid hormone, needs the thyroid hormone in order to function better
  - with growth hormone alone you will be short, without growth hormone but having thyroid hormone your also going to be short

• has direct and indirect actions:
  - directly stimulates the secretion of glucose into the blood and it will directly stimulate the secretion of fatty acids into the blood
  - Insulin Like Growth Factor (IGF) is indirect

• growth hormone is regulated by the hypothalamus
  - anterior pituitary secretes or does not secrete growth hormone based on hypothalamic control
  - hypothalamus secretes two hormones that are antagonistic to one another and regulate growth hormone

Insulin Like Growth Factor (IGF)

• secretion of IGF is stimulated by the GH

• hormone under growth hormone control

• stimulates bone and muscle growth but is regulated by growth hormone

• Indirectly mediates GH

• GHRH and GHIH regulate the secretion of growth hormone by the anterior pituitary there by regulating the secretion of IGF and regulating bone growth and the access to energy sources that support growth

Growth hormone in the hypothalamus

• growth hormone is regulated by the hypothalamus
  - anterior pituitary secretes or does not secrete growth hormone based on hypothalamic control
  - hypothalamus secretes two hormones that are antagonistic to one another and regulate growth hormone
  1. Growth hormone releasing hormone (GHRH)
  2. Growth hormone inhibiting hormone (GHIH)
  - these two hormones are secreted by the hypothalamus and regulate (stimulate or inhibit) the secretion of growth hormone by the anterior pituitary

• GRHR: stimulates the secretion of the growth hormone by the anterior pituitary

• GHIH: antagonistic hormone to GHRH
  - inhibits secretion of growth hormone

• all the releasing hormones are secreted by the hypothalamus and stimulate the secretion of a hormone in the anterior pituitary

Growth Hormone

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