pituitary gland

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Calibri:

Pituitary gland. Dr.Gogoi University of Fiji

Symbol:

The pituitary.

Wingdings:

The pituitary Gland.

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Pituitary Gland Is also known as Hypophysis Sits in the small bony cavity Sella Turcica at the base of the brain. Secretes hormones regulating homeostasis including trophic hormones that stimulate other endocrine glands. 3 lobes-Adenohypophysis also known as the anterior pituitary and the neurohypophysis also known as the Posterior hypophysis.

Pituitary gland.:

Pituitary Gland Also an intermediate lobe that secretes MSH.Rudimentary. Anterior pituitary synthesize and secretes ACTH, LH,FSH,GH,TSH,prolactin. Posterior pituitary secretes oxytocin and ADH. Posterior lobe is connected to the hypothalamus through the pituitary stalk Hormones are actually made in the nerve cell bodies of the hypothalamus and then transported down the posterior pituitary

The pituitary Gland.:

ACTH Is a polypeptide Acts on the adrenal cortex Secreted in response to the corticotropin-releasing hormone (CRH) from the hypothalamus. Consists of 39 amino acids and 13 may be cleaved to (MSH). Hypocortisolism and Addison’s disease have tanned skin. Stimulates the cortex of the adrenal gland to produce corticosteroids, mainly glucocorticoids. Excess ACTH-Addison’s disease Small cell carcinoma Congenital Adrenal hyperplasia Cushing’s syndrome.

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TSH Is a glycoprotein Also known as Thyrotropin 2 subunits α and β α is identical to HCG,LH,FSH β subunit is unique to TSH therefore determines its function. Stimulates thyroid gland to secrete T3, T4 Controlled by Thyrotropin-releasing hormone (TRH)

Pituitary Gland:

Luteinising Hormone A glycoprotein Also known as Lutropin Acts in concert with Follicular stimulating hormone Play a part in normal reproductive function. In females, an acute rise triggers ovulation. In males, stimulates leydig cells to produce testosterone. Controlled by Gonadotropin-releasing hormone.

Pituitary Gland:

Follicle Stimulating Hormones. A glycoprotein. Acts in synergy with LH. In women, stimulates the growth of immature Graafian follicles to maturation. In men, enhances production of sperm cells. Half life of 3-4 hrs. Controlled by Gonadotrophin-releasing hormones . High in menopause and low in childhood. High levels is indicative of defective feed-back from the gonads.

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FSH (ctd) High levels is typical in menopause, but abnormal in reproductive years and may be a sign of------- Premature menopause Gonadal dysgenesis, Castration. Testicular failure. Low levels is seen in.. Kallman syndrome Hypopituitarism Hypothalamic causes Drugs-GnRH antagonists.

ACTH:

Prolactin A peptide hormone Associated with lactation. In breast feeding, suckling reflex—prolactin production—Fills breast with milk (lactogenesis) Production is regulated by neuroendocrine neurons of the hypothalamus.

TSH:

They are Classified into: Somatotropic Hormones: 1- Growth Hormone (GH). 2- Prolactin (Prl). 3- Placental Lactogen (PL). Glycoprotein Hormones: 1- Luteinizing Hormone (LH). 2- Follicle-Stimulating Hormone (FSH). 3- Chrionic Gonadotropin (CG). 4- Thyroid-Stimulating Hormone (TSH). P ro- O pio m elano c ortin (POMC) derived Hormones: 1- Corticotropin: ACTH. 2- Melanocyte-Stimulating Hormones: a -MSH, b -MSH. 3- Lipotropins: b -LPH,  -LPH

Luteinising Hormone:

Growth Hormone (GH) Structure: It is a single polypeptide chain composed of 191 amino acid residues. It has two disulfide bonds.

Follicle Stimulating Hormones.:

Growth Hormone Also known as Somatotropin. A protein hormone. Stimulates growth and cell production. Excess GH leads to acromegaly and Gigantism. Highest amount of GH is secreted during puberty. Regulated by GHrH and somatostatin. Other stimulators are.. Sleep, exercise, Reduced blood sugar, dietary protein, estradiol. Inhibitors are ..somatostatin, circulating GH, Dietary carbohydrates, glucocorticoids.

FSH (ctd):

Secretion: Somatotropes of the Anterior Pituitary. Level: High in children. Maximal during adolescence. Lowest during adulthood. Measurments: During 24 hours. After stimulation. Regulation: Stimulation: By Growth Hormone Releasing Hormone (GHRH). Inhibition: By Somatostatin.

Prolactin:

Physiological Effects: Direct Effects: 1- Stimulation of Lipolyses (Hydrolyses of Triglycerides). 2- Stimulation of Hepatic glucose output. 3- Production of Insulin-like growth factors (IGF’s, Somatomedins) Indirect Effects: Mediated by IGF-1: 1- Increase cell numbers. 2- Positive Nitrogen balance. 3- Increase Protein synthesis.

They are Classified into::

Growth Hormone (GH) peptide hormone produced in the anterior pituitary both a hormone and a trophic factor chemical structure different between species - stimulates release of insulin-like growth factors (IGFs; somatomedins)

Growth Hormone (GH):

Effect on Growth growth hormone is only one necessary factor for normal development thyroid hormone androgens estrogens insulin IGFs

Growth Hormone:

Bone Development GH stimulates long bone growth IGFs stimulate both bone and cartilage growth increases length prior to epiphyseal closure increases width after epiphyseal closure

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Metabolic effects of Growth Hormone Increased rate of protein synthesis in all body cells Increased mobilization and use of fatty acids from adipose tissue for energy Decreased rate of glucose utilization throughout the body (i.e. enhances body protein, uses up fat stores and conserves CHO)

Physiological Effects::

Growth Hormone Deficiency in childhood, results in pituitary dwarfism both respond to GH therapies complete deficiency partial deficiency

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Growth Hormone Excess in childhood leads to GIGANTISM

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Growth Hormone Excess in adulthood leads to ACROMEGALY

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Regulation of GH secretion released in a pulsatile fashion in response to GHRH release from the hypothalamus, inhibited by GHIH release also stimulated by: hypoglycemia and fasting increased amino acids in plasma stress exercise

Metabolic effects of Growth Hormone:

Metabolic Effects of Growth Hormone GH is anabolic increases fat breakdown increases hepatic glucose output

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Disease Conditions Related to GH: Deficiency: * Dwarfism. Excessive Secretion: * Giantism: Due to tumor in somatotrpes in young children or adolescents. * Acromegaly: Rare disease (3/Million). Causes: 1- Benign tumor of Pituitary gland (90%). 2- Tumors of pancreas, lung or adrenal gland. Symptoms: Enlargements of extremities.

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Growth Hormone Releasing Hormone (GHRH) Structure: Single polypeptide chain composed of 108 amino acid residues. Function: Stimulate the secretion of GH. Uses: Treatment of children with GH deficiency due to hypothalamic defects. Diagnoses of the cause of GH deficiency.

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Regulation of GH GH release is stimulated by the GHrH Which act on somatomedins(IGF-1 somatomedinC) Act to increase growth of cells, cartilage and protein metabolism. GH release is inhibited by Somatostatins which are produced in the hypothalamus. Secretion of somatostatins is stimulated by increased circulating levels of GH. Other sites where we find somatostatins are the GIT and pancreas.

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Gigantism

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Acromegaly

Disease Conditions Related to GH::

Dwarfism Can be due to GHrH deficiency, GH deficiency or other cause. Extreme shortness But proportional body parts. Other causes not due to pituitary GH are osteodystrophy, achondroplasia.

Growth Hormone Releasing Hormone (GHRH):

Hormones of the Posterior Pituitary antidiuretic hormone (ADH), oxytocin neurohormones synthesized by neurons in the supraoptic and paraventricular nuclei small peptides synthesized in the cell bodies and transported to the posterior pituitary by specific carrier proteins

Gigantism:

Herring Bodies Neurophysin-I (oxytocin) Neurophysin-ii (ADH)

Acromegaly :

Antidiuretic Hormone (ADH) antidiuretic actions vasopressor actions increases permeability of the collecting ducts to water V 2 receptors constricts vascular smooth muscle cells V1 receptors, non-hormonal

Dwarfism:

Antidiuretic Hormone A peptide hormone. Also known as vasopressin. Released during dehydration. Regulates retention of water within the body. Act by increasing the permeability of the collecting duct to water and allows water reabsorbtion and excretion of small volume of concentrated urine. Also induces moderate vasoconstriction. Regulation—Reduced plasma volume---increased production. Other influences are caffeine and ethanol which reduces secretion. Angiotensin II stimulates secretion.

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diabetes insipidus

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Control of ADH Release Osmotic pressure: Volume effects: Others: - secretion parallels osmotic pressure as ECF drops, ADH secretion increases baroreceptor mediated - pain, trauma, emotion, alcohol

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Oxytocin breast-feeding childbirth (parturition) contracts the myoepithelial cells of the alveoli classic neuroendocrine reflex in late pregnancy, uterine smooth muscle (myometrium) becomes sensitive to oxytocin positive feedback

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Oxytocin In females, released in large amounts after distension of the cervix and vagina during labor. Actions. let-down reflex and uterine contraction in lactating mothers. Acts on the mammary glands causing milk let-down into collecting chamber where it is extracted by suckling the nipple. Suckling produces stimulation of the neurons that make oxytocin to fire action potential which results in pulses of oxytocin from the pituitary.

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Oxytocin Also important for uterine contraction—important for cervical dilatation before birth at the 2 nd and 3 rd stages of labor. During breastfeeding, causes mild but painful contractions of the uterus during the first few weeks of lactation. Other actions.. sexual arousal and bonding-monogamous pair bond.

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Pituitary insufficiency The changes that develop in pituitary insufficiency are predictable in terms of the known hormonal functions of the gland In hypopituitarism, the adrenal cortex atrophies. They develop reduced glucocorticoids and sex hormones. Initially,no mineralocorticoid deficiency Growth is inhibited, Thyroid function is depressed The gonads atrophy Sexual cycles stop Some secondary sexual characteristics disappear.

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Pituitary Hyper function Usually due to tumors of the pituitary Cause symptoms of hyper secretion of the hormones.

Pituitary insufficiency:

Pharmacology of the Hypothalamus & Pituitary Gland:

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