Pituitary gland

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 PITUITARY GLAND 

The pituitary gland (hypothesis) is a small gland situated at the base of the skull in the sella turcica and connected to the brain by pituitary stalk It is divided into

 1. Anterior pituitary (adenohypophysis)

 2. posterior pituitary (neurohypophysis).

 3. Intermediate lobe (called pars intermedia)


Hypothalamo- Hypophysial connections

  Two types of connections b/w hypothalamus and pituitary gland 

 1- A vascular connections between hypothalamus and anterior pituitary gland in the form of a hypothalamo-hypophysial portal circulation 

 2- A nervous connection between the hypothalamus and posterior lobe in the form of hypothalamo- hypophysial tract

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Anterior Pituitary Gland 

 It is called the “Master gland

 It is essential for life 

 It secrete the following hormones

Dr. Eman El Eter The pituitary Gland: Anterior pituitary hormones. Posterior pituitary hormones. - ppt download” 

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Anterior Pituitary Hormones

 I-Polypeptide Hormones

 1. Growth Hormone (GH, Somatotropin): primary hormone responsible for regulating body growth, and is important in metabolism

2. Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex

 3. Prolactin: Females: stimulates breast development and milk production. Males: involved in testicular function.

11- Glycoprotein Hormones

 1. Follicle-stimulating Hormone (FSH): Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries. Males: required for sperm production

 2. Luteinizing Hormone (LH): Females: responsible for ovulation, formation of corpus luteum in the ovary, and regulation of ovarian secretion of female sex hormones. 

Males: stimulates cell in the testes to secrete testosterone

 3. Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland

GROWTH HORMONE

  It is a small protein hormone (191a.a). 

 It causes growth of all tissues of the body including bone, muscles & viscera( except nervous tissue).  It increased size of the cell & mitosis with development of large number of cells(i.e increase in tissue size; length& weight) .

 It exerts its action by direct and indirect mechanism. 

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Cellular mechanism of action of GH (direct effect)

Activation of the cytoplasmic Portion of the receptors Which has tyrosine kinase activity that→ Stim. DNA transcription→ formation of mRNA & tRNA→ promote protein synthesisFrontiers | Growth Hormone and Insulin-Like Growth Factor Action in Reproductive Tissues | Endocrinology

(indirect effect)

 Anterior Pituitary Gland - ppt video online download

Functions of GH:-

  1-Effect on growth:

  GH stim growth of all tissues, It increase numbers, size & differentiation of cells.

  Insulin & chat are necessary for action of growth hormone . 

  Somatomedin stim. epiphyseal cartilage & elongation of bone before puberty

  After puberty increase bone thickness by stim. of osteoblast

II-Metabolic functions:

 A) On protein: Anabolic effect

  1-GH increases transport of amino acid through cell membrane to interior of the cell. 

  2-GH increase protein synthesis by the ribosome, .

  3-GH stimulates the transcription of DNA in the nucleus causing formation of large quantities of RNA .This promotes protein synthesis & also promotes growth.

  4-GH decreases catabolism of protein & amino acid (protein sparer).

B) On fat: Lipolytic effect 

 GH has a lipolytic effect, it increase utilization of fat leading to release of fatty acids from adipose tissue to the body fluids. 

C) On carbohydrates (It is diabetogenic hormone): 

 1- It decreases utilization of glucose for energy; may result from the increased mobilization & utilization of fatty acids for energy. 

2- It increases glycogen deposition. The glucose that does enter the cells is rapidly changed to glycogen 3- It diminishes uptake of glucose by the cells.

4-It decreases the number of insulin receptor.

III-Other functions: 

 1-It stimulates erythropoiesis. 

 2-It increases gastrointestinal absorption of calcium. 

 3- It decreases the rate of urinary excretion of Na+&K+ ions b/c these electrolytes are needed for the growing tissue .

What Does the Pituitary Gland Do? | Pituitary Gland Function & Hormones

Pituitary Gland - Function and Hormone Production

To be cont...

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