Endocrinology Take Home Exam

 

SALUMBRE, Renz L. ZOO 225: Endocrinology I. MECHANISM OF HORMONE ACTION 1. Follicle Stimulating Hormone (FSH)

A pep peptide tide hormon hormone e rel release eased d by the fol follicu liculot lotrop rophic hic cel cells ls in the ant anterio eriorr pituitary. Its primary role is the development of major reproductive processes in both male and female. In the male, FSH develops and maintains the male phenotype along with otherr and othe androne ronergic rgic stero steroid id horm hormone ones. s. An exampl example e of thi this s is its acti action on on Serto Sertolili cells to promote sperm formation. In the female, FSH acts on thecal cells and Ovarian granulosa to promote the maturation of ovarian follicle and also to stimulate estrogen production. Source: nd

Norman, A.W. & G. Litwack. 1997. 1997 . Hormones (2 Hormones (2 ed.). Academic Press : USA.

2. Thyroid Stimulating Hormone (TSH)

TSH TS H con control trols s thy thyroi roid d cell gro growth wth and hor hormone mone pro produc duction tion by bind binding ing to specific receptors located on the basolateral cell membrane of a thyroid cell. And also stimulates stimulates the met metabo abolism lism of iod iodine. ine. Upo Upon n bind binding, ing, it acti activat vates es camp and phospho phos phoinos inosito itoll path pathwa way y for sig signal nal tran transdu sductio ction. n. Its acti actions ons are also medi mediate ated d through the G-protein-adenylyl-cyclase-cAMP system and possibly through the phosphatidylinositol system (that then results in the increase of calcium). Source: Cooper, D.S., F.S. Greenspan & P.W. Ladenson. The Thyroid Gland . In Gardner, D.G. & D. th

Shoback. 2007. Greenspan’s Basic & Clinical Endocrinology (8 Endocrinology  (8 ed.). McGraw-Hill : USA.

3. Testosterone 1

 

Testost estosterone erone is the major male androgen hormone that induces activity of the Sertoli cells found in the seminiferous seminiferous tubules. Leydig cells secret secrete e testosterone. The biological effects of testosterone are well documented. Some of these are: (a) diff differe erentia ntiation tion of the male rep reprod roducti uctive ve sys system tem;; (b) skelet skeletal al mus muscle cle growth gro wth and larynx dev develop elopment ment and othe otherr sec seconda ondary ry sexua sexuall cha charact racteris eristics tics.. Testosterone also accounts for male behavior. Testosterone is free and unbound or may be bound to serum proteins if it enters circulation. One of the major binding proteins is sex hormone-binding globulin glob ulin (SHB (SHBG). G). Onc Once e tes testos toster terone one lea leave ves s cir circula culation tion,, it is con convert verted ed into into dihydrotestosterone by an isoenzyme. Source: Braunstein, G.D. Testes . In Gardner Gardner,, D.G. & D. Shoback. Shoback. 2007 2007.. Greenspan’s Basic & Clinical  th

Endocrinology (8 Endocrinology  (8 ed.). McGraw-Hill : USA. Jameson, E.W. 1988. Vertebrate Reproduction. John Wiley & Sons : USA.

4. Parathyroid Hormone

Parathyroid hormone or Parathormone is secreted by parathyroid glands. It acts to increase the calcium levels in the blood through the promotion of kidney retention of calcium. This Th is ho hormo rmone ne act act in tw two o wa ways ys:: (1) (1) It indu induces ces tissu tissues es (suc (such h as kidn kidney ey tubule tub ules, s, bon bone, e, an and d inte intesti stine ne)) to relea release se calci calcium um in the bloo bloodst dstre ream; am; (2) it facilitates excretion of phosphate into the urine even if PTH promotes calcium reabsorption into the kidney tubule. These two actions primarily raise the amount of plasma levels of calcium and concomitantly lower phosphate levels. Source: Fried, G.H. & G.J. Hademenos. 1999. Schaum’s Outline of Theory and Problems of Biology (2 Biology  (2

nd

ed.). McGraw-Hill : USA.

5. Insulin

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Insulin is a peptide hormone released by B cells found in the islets of Langerha Lang erhans ns of the pan pancre creas as in res respons ponse e to ele elevat vated ed bloo blood d gluc glucose ose lev levels. els. Glucagon acts on the liver cells to decrease glucose levels in the blood. Once blood bloo d glu glucose cose is dec decrea reased, sed, it fee feeds ds back on B cell cells s to halt the secre secretio tion n of insulin. Somatostatin inhibits further secretion of insulin. Source: Van De Graaff, K.M. & R. W. Rhees. 1997. Schaum’s outline of Theory and Problems of Human nd

Anatomy and Physiology (2 ed.). McGraw-Hill : USA. th

Randall, D., W. Burggren & K. French. 2002. Eckert Animal Physiology (5 Physiology (5 ed.). W.H. Freeman and Company : NY, USA.

6. Kidney Hormones

A variety of hormones act on the kidney, which is the major organ for the regulation of water and electrolyte balance in the body. These hormones are: Antidiuretic hormone (vasopressin) regulates water turnover and its primary action acti on is to inc increas rease e wa water ter rea reabsor bsorptio ption. n. ADH ach achiev ieves es wa water ter rea reabso bsorptio rption n by increasing the water (from urine) permeability of the kidney collecting ducts. ADH originates from the posterior pituitary gland and is stimulated by the increase plasma osmotic pressure or a decrease in blood volume. Atrial natriuretic peptide originates from the atrium and acts on the kidneys by reducing sodium and water absorption. Increased venous pressure stimulates release of this hormone. The parafollicular cells of the thyroid secrete calcitonin. It acts on both kidneys and bone by decreasing the release of calcium ions from bone and, in the kidney, increases renal calcium and phosphate excretion. Increased levels of plasma calcium stimulate further secretion. Mineralocorticoids, such as aldosterone, come from the adrenal cortex and target targ et the dis distal tal kidn kidney ey tubu tubules, les, with ang angiot iotens ensin in II stim stimulat ulating ing its rel release. ease. Mineralcorticoids are steroid hormones that function to promote sodium reabsorption from the urinary filtrate. Parathyroid hormones also act on the kidneys by decreasing renal calcium excretion. 3

 

Source: th

Randall, D., W. Burggren & K. French. 2002. Eckert Animal Physiology (5 Physiology (5 ed.). W.H. Freeman and Company : NY, USA.

7. Intestinal Hormones

There are two hormones active in the intestine. One is secretin, which is released from the duodenal mucosa stimulated by acid digestion. Bayliss and Starling demonstrated that this hormone’s release elicits the flow of digestive enzymes from the pancreas. The second digestive hormone is cholecytoskinin. This hormone is similar to secretin in that it is released from the mucosal lining of the duodenum. Cholecytoskinin maintains a steady flow of bile from the gallbladder.

Source: Fried, G.H. & G.J. Hademenos. 1999. Schaum’s Outline of Theory and Problems of Biology (2 Biology  (2

nd

ed.). McGraw-Hill : USA.

8. Adrenaline

Adrenaline (epinephrine) is both hormone and amines and is responsible for flight-or-fight situations. This hormone is commonly associated with the adrenal medulla and exhibits a variety of effects that prepares the body when in stress. Such actions on the body are: (a) elevation of blood pressure by increasing cardiac output and peripheral vasoconstriction; (b) acceleration of the respiratory rate rat e and the sub subsequ sequent ent dila dilation tion of res respira piratory tory pass passage agewa ways; ys; (c) incr increas eased ed muscula musc ularr con contrac traction tion;; (d) incr increas ease e rat rate e of gly glycog cogen en bre breakd akdown own into gluc glucose ose resulting in high blood glucose level; (e) increase in the conversion of fats into fatty acids resulting in high blood fatty acids; and lastly, (f) increase release of adenocorticotrophic hormone and thyroid stimulating hormone from the anterior pituitary. Source:

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Van De Graaff, K.M. & R. W. Rhees. 1997. Schaum’s outline of Theory and Problems of Human nd

Anatomy and Physiology (2 ed.). McGraw-Hill : USA.

II. SYMPTOMS OF DISORDERS/DISEASES OR HYPER/HYPO-SECRETION `

1. Growth Hormone

Dwarf Dw arfism ism is a commo common n ma manif nifes estat tation ion of a grow growth th ho hormo rmone ne sec secre retio tion n disorder. This is characterized by having a decreased growth hormone before the normal height has been reached. A person afflicted with this disorder exhibits a small body but normally proportioned; mild obesity with lack of appetite; tender and thin skin. This particular disorder can be treated using injection of growth hormone. Gigantism is a condition wherein growth hormones are produced in excess befo be fore re clo closu sure re of the ep epip iphy hyse seal al grow growth th plat plates es in long long bo bone nes. s. Sy Sympt mptom oms s presented by an individual include a pathological acceleration of growth; also, if tumors are found in the pituitary, it may cause impaired vision. Treatment is through surgical removal of the tumor of the pituitary gland. Acromegaly occurs when excess growth hormone are produced after the closure clos ure of the epip epiphys hyseal eal pla plates tes.. The sympto symptoms ms pre presen sented ted by an indi individu vidual al include enlarged jaw; thickened and puffy nose; increased basal metabolic rate; and loss of visual fields. Treatment includes irradiation, radioisotope implantatio, or surgical removal of the tumor in the pituitary gland (if present) or the surgical removal of the pituitary gland itself. Source: Van De Graaff, K.M. & R. W. Rhees. 1997. Schaum’s outline of Theory and Problems of Human nd

Anatomy and Physiology (2 ed.). McGraw-Hill : USA.

2. Antidiuretic Hormone

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) occurs when whe n ant antidiu idiuret retic ic horm hormones ones are pro produce duced d in exces excess. s. Thi This s caus causes es the body to retain ret ain water with certain certain lev levels els of the electro electrolyts lyts to fall. fall. SIAD SIADH H is comm common on in people with heart failure or those afflicted with a diseased hypothalamus. Also 5

 

certain cancers may also trigger SIADH. The symptoms of this condition include nausea, seizures and coma. It may also trigger behavioral changes such as irritability, competitiveness, confusion, hallucination and stupor. Medication includes ADH-suppressants and regulation of fluid intake.

Diabetes insipidus is another condition associated with the deficiency of ADH in circulation. This condition may be considered heritable associated with diabetes diabet es mellitus, optic atroph atrophy y and sensorineural deafness. Secondary conditions also pose the possibility of acquiring diabetes insipidus such as head injury,, pituitary surgery, tuberculosi injury tuberculosis s and other granulomatous diseases, infection, tumors, etc. Often symptoms of this disease includes increase fluid intake, inta ke, hy hyperto pertonic nicity ity and incr increas eased ed uri urinati nation on (in chi childre ldren, n, it may cau cause se bed bed-wetting). Source: Diabetes Diabet es

Insipidus Insipidus Foundatio Foundation. n.

2006. Symptom Symptoms s

of

Diabetes Diabetes Insipidus. Insipidus. Retriev Retrieved ed

at

http://www.diabetesinsipidus.org/symptomsofdi.htm Gardner, D.G. Endocrine Emerencies. In Gardner, D.G. & D. Shoback. 2007. Greenspan’s Basic  th

& Clinical Endocrinology (8 Endocrinology (8 ed.). McGraw-Hill : USA. Health System. 2004. Diabetes and other Endocrine and Metabolic Disorders. University of Virginia. Retrieved at http://www.healthsystem.virginia.edu/uv http://www. healthsystem.virginia.edu/uvahealth/peds_diabetes/siadh.cf ahealth/peds_diabetes/siadh.cfm m

3. Mineralocorticoids

Hypera Hyp eraldos ldoster teronis onism m is a con conditi dition on cau caused sed by exces excessiv sive e pro produc duction tion of aldosterone. aldoste rone. Hyper-s Hyper-secreti ecretion on of aldost aldosterone erone may also be influenc influenced ed by high re renn nnin in le leve vels. ls. Th This is cond conditi ition on is mos mostt com common mon in femal females es tha than n in ma males les an and d usually result in hyperte hypertension. nsion. Excessiv Excessive e levels of aldost aldosterone erone act on the distal renal tubule promoting sodium retention, which then results in water retention and volume expansion with hypertension. Potassium is also secreted and may result in hypokalemia. Other symptoms may include polyuria, headache and lethargy. The condition wherein a decrea decreased sed levels of aldoste aldosterone rone is called hypoaldosteronism, or hyporeninemic hypoaldosteronism. This occurs in geriatric patients who are already suffering from diabetes and mild renal insufficiency. 6

 

However, patients appear asymptomatic but hyperkalemia and acidosis may be detected during screenings. Hyperkalemia may pose a threat in that it can cause a heart block upon administration of beta-andrenergic blocking agent. If hyperkalemia does not occur, fludcortisone or furosemide may be used to treat hypoaldosteronism coupled with potassium-restricted diet. Source: Greenspan, S.L. & N.M. Resnick. Geriatric Endocrinology. In Gardner, D.G. & D. Shoback. 2007. th

Greenspan’s Basic & Clinical Endocrinology (8 Endocrinology  (8 ed.). McGraw-Hill : USA. Patient UK. 2008. Hyperaldosteronism. Retrieved at http://www.patient.co.uk/showdoc/40000954/.

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