DISORDERS OF ANTERIOR AND POSTERIOR PITUITARY GLAND

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the presentation is about the normal physiology of pituitary gland and disorders associated with it

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DISORDERS OF ANTERIOR AND POSTERIOR PITUITARY HORMONES:

DISORDERS OF ANTERIOR AND POSTERIOR PITUITARY HORMONES PRESENTERS: ZECHARIAH MALOU NE CHOL OBSE&GYNE MUHAS

OVERVIEW:

OVERVIEW Introduction Anterior pituitary hormones and their Disorders Posterior pituitary hormones and their Disorders conclusion References

INTRODUCTION:

INTRODUCTION The pituitary gland (hypophysis) is a small pea shaped gland—about 1 cm in diameter and 0.5 to 1 gram in wt. pituitary gland lies in the sella turcica , a bony cavity at the base of the brain It is connected to the hypothalamus by the pituitary (or hypophysial) stalk.  

Pituitary introduction cont…:

Pituitary introduction cont… Physiologically, the pituitary gland is divisible into two distinct portions: the anterior pituitary( adenohypophysis) posterior pituitary( neurohypophysis) Between these is a small, relatively avascular zone called the pars intermedia

Anterior Pituitary (adenohypophysis):

Anterior Pituitary (adenohypophysis) SECRETES 6+ HORMONES: ACTH (adrenocorticotropic hormone) aka (corticotrphin) release of cortisol in adrenal glands TSH (thyroid stimulating hormone) aka (thyrotropin) release of T3 & T4 in thyroid gland GH (growth hormone) aka (somatotropin) stimulates growth of bone/tissue

Slide7:

FSH (follicle stimulating hormone) stimulates growth of ovarian follicles & spermatogenesis in males LH (lutenizing hormone) regulates growth of gonads & reproductive activities Prolactin aka (luteotropin/mammotropin) promotes mammary gland growth and milk secretion ANTERIOR PITUITARY (adenohypophysis)

Anterior pituitary Disorders:

Anterior pituitary Disorders ETIOLOGY Primary : the defect is in the gland itself which releases that particular hormone that is too much or too little. Example: Secondary : defect is somewhere outside of gland i.e. GHRH from hypothalamus TRH from hypothalamus

GROWTH HORMONE:

GROWTH HORMONE Secretion controlled by hormones from hypothalamus: Growth hormone–releasing hormone (GHRH),-stimulates release of GH Growth hormone inhibitory hormone ( somatostatin ) -inhibits release of GH GH Exerts Much of Its Effect directly on almost all tissues of the body Through Somatomedins (IGF)

Slide10:

Growth hormone causes the liver (and, to a much less extent,other tissues) to form small proteins called somatomedins. somatomedin effects on growth are similar to the effects of insulin on growth. Therefore the somatomedins are also called insulin-like growth factor(IGFs).

Slide11:

IGF II (relaxin)-exert effects on fetal life Somatomedin C (also called IGF-I).-after delivery

Functions of Growth Hormone :

Functions of Growth Hormone ↑ rate of protein synthesis in most body cells and Promotes Protein Deposition in Tissues mobilization of fatty acids from adipose tissue and↑ use of fatty acids for energy; carbohydrate metabolism through(1)↓glucose uptake in tissues (2) gluconeogenesis in the liver, (3) increased insulin secretion Growth Hormone Stimulates Cartilage and Bone Growth

DISORDERS OF GH:

DISORDERS OF GH GH deficiency deficiency of GH leads to Dwarfism. 2/3 of dwarfs results from panhypopituitarism during childhood. 1/3 of dwarfs, with only GH deficient. African pygmy dwarfs and the Lévi-Lorain dwarfs, the level of GH secretion is normal or high, but there is a hereditary inability to form somatomedin C  

GH excess :

GH excess Gigantism results from production of large quantities of growth hormone before adolescence before epiphyseal plate fuses with the bone shaft. All body tissues grow rapidly. height increases and →→giant. Giants will have hyperglycaemia 10% will develop diabetes mellitus.

GH excess cont… :

GH excess cont… Acromegaly. Excessive growth hormone production after puberty the bones can become thicker and the soft tissues continue to grow. Enlargement is especially marked in the bones of the hands and feet and in the membranous bones, including the cranium, nose, bosses on the forehead, supraorbital ridges, lower jawbone, and portions of the vertebrae(resulting to kyphosis) soft tissue such as the tongue, the liver, kidneys, become greatly enlarged

THYROID STIMULATING HORMONE (TSH):

THYROID STIMULATING HORMONE (TSH) Secretion controlled by Thyrotropin-releasing hormone (TRH ) TSH influences thyroid structure and function by: The number & size and secretory activity of cells Iodine trapping Proteolysis of thyroglobulin Structural and functional changes by TSH is mediated by c-AMP

TSH DISORDERS:

TSH DISORDERS TSH Deficiency Secondary hypothyroidism Results from TSH or TRH deficiency Thyrotrophin deficiency alone is rare. It is usually associated with deficiency of other adenohypophysial hormones exhibits identical symptoms to primary thyroid disease . Hypothyroidism From TSH deficiency differs from other causes by having low levels of TSH,T3 and T4 in the blood.

TSH Deficiency cont… :

TSH Deficiency cont… Cretinism cretins are hypothyroid from birth They are dwarfed and mentally retarded and have potbellies and enlarged, protruding tongue Causes maternal iodine deficiency congenital abnormalities of the fetal hypothalamo–pituitary–thyroid axis maternal antithyroid antibodies that cross the placenta and damage the fetal thyroid

Hyperthyroidism :

Hyperthyroidism Results from TSH-secreting pituitary tumor . Leads to thyroid over activity hence increased T3 and T4 levels in blood. Hyperthyroidism From TSH excess differs from other causes by having high levels of TSH,T3 and T4 in the blood.

ACTH:

ACTH Secretion controlled by Corticotropin-releasing hormone (CRH)     ACTH necessary maintenance adrenal structure and function by 1. Stimulates production of glucocorticoids and androgens by the adrenal cortex 2. maintains size of zona fasciculata and zona reticularis of adrenal cortex

DISORDERS OF ACTH:

DISORDERS OF ACTH    ACTH deficiency characterized by a decrease in adrenal androgens and cortisol. Symptoms of cortisol deficiency are nearly identical to those of 1°adrenal insufficiency, but can be differentiated by lack of skin hyper pigmentation.(in synthesis,ACTH shares a precursor with a hormone Melanocyte Stimulation Hormone (MSH) also pts will have ↓axillary and pubic hair(↓adrenal androgens

Confused about cushing syndrome and disease!?:

Confused about cushing syndrome and disease!? Any condition that causes the adrenal gland to produce excessive cortisol results in the disorder Cushing's syndrome Causes;- adenomas of the anterior pituitary -abnormal function of the hypothalamus that causes ↑ levels of CRH -secretion of ACTH by a tumor elsewhere in the body, such as abdominal and lung carcinoma.

Slide23:

ACTH is normally produced by the pituitary gland When a pituitary tumor secretes excessive ACTH, the disorder resulting from this specific form of Cushing's syndrome is referred to as Cushing's disease.

GONADOTROPIC HORMONES (LH AND FSH):

GONADOTROPIC HORMONES (LH AND FSH ) Secretion controlled by Gonadotropin-releasing hormone (GnRH) Luteinizing hormone (LH ) : Stimulates testosterone synthesis in Leydig cells of testes; stimulates ovulation, formation of corpus luteum, and oestrogen and progesterone synthesis in ovaries. Follicle-stimulating hormone (FSH) Stimulates development of ovarian and follicles regulates spermatogenesis in the testis

GONADOTRPIN DISORDERS  :

GONADOTRPIN DISORDERS   Deficiency of FSH and LH In men will present as symptoms of low testosterone levels such as: ↓ libido, erectile dysfunction long-standing hypogonadism have ↓pubic hair growth, soft testes, and gynecomastia. Patients may be anaemic due to ↓ erythropoietin production, which causes a normochromic, normocytic anaemia.

Deficiency of FSH and LH cont… :

Deficiency of FSH and LH cont… Premenopausal women present with altered menstrual function, hot flashes, decreased libido, breast atrophy, vaginal dryness. Pubic and axillary hair growth is usually normal unless a concomitant ACTH deficiency exists. Low FSH and LH levels increase risk of osteoporosis

PROLACTIN:

PROLACTIN Secretion is controlled by Prolactin inhibitory hormone (PIH), Prolactin Promotes development of the female breasts and secretion of milk. Prolactin in blood rises 10 to 20 times the normal level from the 5 th wk. of pregnancy until delivery.

PROLACTIN DISORDERS:

PROLACTIN DISORDERS Hyperprolactinemia , Abnormally-↑ levels of prolactin in blood. normal level < 580 mIU/L for women, and <450 mIU/L for men Inhibits secretion of gonadotropin releasing hormone (GnRH) by increasing the release of dopamine from the arcuate nucleus of the hypothalamus therefore inhibiting gonadal steroidogenesis.

Hyperprolactinaemia cont…:

Hyperprolactinaemia cont… Symptoms : In women , ↓Oestrogen -which presents as anovulatory infertility, irregular menses→ amenorrhoea, loss of libido, vaginal dryness, osteoporosis. breast pain and galactorrhoea (in non pregnant /not breastfeeding) In men , decreased libido, erectile dysfunction infertility and gynecomastia

Prolactin deficiency :

Prolactin deficiency Partial isolated prolactin deficiency is rare, and may have a genetic component (i.e, familial puerperal alactogenesis). Prolactin deficiency mostly occur in panhypopituitarism

POSTERIOR PITUITARY GLAND:

POSTERIOR PITUITARY GLAND The posterior pituitary gland is composed mainly of glial -like cells called pituicytes. The pituicytes do not secrete hormones; they act as a supporting structure for large numbers of terminal nerve fibres and terminal nerve endings from nerve tracts that originate in the supraoptic and paraventricular nuclei of the hypothalamus,. The nerve endings are bulbous knobs that contain many Secretory granules.

Post pituitary cont…:

Post pituitary cont… These endings lie on the surfaces of capillaries, where they secrete two hormones: (1) antidiuretic hormone ( vasopressin) Mainly secreted from the SON (2) Oxytocin Mainly secreted from the PVN

ANTI DIURETIC HORMONE:

ANTI DIURETIC HORMONE ADH Increases water reabsorption in kidneys and intestines. Actions mediated through cAMP Actions can be inhibited by alcohol, diuretics , destruction of the hypothalamus or the posterior pituitary and Inhibition on adenyl cyclase or receptors Stimulated by high osmolarity, low pressure,hypovolaemia.

ADH DISORDERS:

ADH DISORDERS ADH deficiency Diabetes Insipidus Results from inability to produce or release ADH from the posterior pituitary Causes: congenital, head injuries or infections. distal tubular segments cannot reabsorb water in the absence of ADH → polyuria with urine volumes that can > 15 L/day.

Diabetes insipidus cont…:

Diabetes insipidus cont… Diabetes insipidus could be : Neurogenic -deficiency of ADH Nephrogenic -deffective or absence of ADH receptors in distal tubules.

ADH excess:

ADH excess Syndrome of Inappropriate Antidiuretic Hormone Secretion Results from excessive ADH prod.from tumours(pituitary,lung ADH ↑ reabsorption of water → concentrated urine. Free water absorption causes hyponatremia

OXYTOCIN:

OXYTOCIN Oxytocin functions Powerfully stimulates contraction of the pregnant uterus especially toward the end of gestation. contraction of myoepithelium of the lactating mammary gland which leads to ‘ milk letdown’ or milk ejection.

Oxytocin disorders:

Oxytocin disorders Oxytocin deficiency Psychogenic factors in the body of the lactating mother can inhibit oxytocin secretion and consequently depress milk ejection.

MEDICAL CORRELATION:

MEDICAL CORRELATION Sheehans syndrome It is a rare complication of pregnancy Pathophysiology: 1.Hypertrophy and hyperplasia of lactotrophs during pregnancy results in the enlargement of the ant. pituitary without a corresponding ↑in blood supply. 2.the anterior pituitary is supplied by a ↓ pressure portal venous system. due to those reasons, hypotension due to blood loss can easily lead to necrosis

CONCLUSION:

CONCLUSION A decreased in secretion of all the anterior pituitary hormones leads to Panhypopituitarism . causes: congenital or acquired e.g. trauma, radiation,sheehans syndrome. Pt will present with deficiency of all adenohypophysial hormones.

Quick reminder:

Quick reminder

REFERENCES:

REFERENCES Guyton & Hall Textbook Of Medical Physiology 11th Ed Review of medical physiology by W.Ganong www.wikipedia.org

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