Kuliah Endokrin
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Transcript of Kuliah Endokrin
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Survey of Some Human Endocrine Glands
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Endocrine organs
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Central Roles of the Hypothalamus and Pituitary
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Pituitary Dwarfism
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Gigantism and Acromegaly
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Action of Steroid Hormones
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Action of Peptide Hormones
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Thyroid Gland P618-623located over tracheainferior to larynx
Hormones:Thyroid hormoneCalcitoninF16.7
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anterior pituitaryparaventricular nucleusThyroid
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Synthesis and secretion
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Oxidization and organification
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Clinical uses of thyroid hormoneLevothyroxine (synthetic T4) Drug of choice for routine replacement therapyIdentical to endogenous T4 and converted to T3Long half-life allows once daily oral administrationLiothyronine (synthetic T3) Rapid absorption, shorter T1/2 spiking, uneven blood levels, transient actionFrequent dosing requiredUse limited to situations requiring rapid response
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Hyperthyroidism (thyrotoxicosis)Characterized by: Increased cardiac outputNervousness Muscle weaknessIncreased BMRHyperglycemiaHypocholesterolemiaWeight lossGraves' disease:Most common form of hyperthyroidismThyroid-stimulating immunoglobulins (TSIg) interact with the TSH receptor, activate the thyroidSymptoms: Diffuse goiterExophthalmus - protruding eyes, mucopolysaccharide infiltration of the extraocular tissueOther signs of hyperthyroidism (above)
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HypothyroidismCharacterized by: decreased cardiac output slow mental functionmuscle fatiguehypoglycemiadecreased body temperature
Causes:Primary hypothyroidism:Hashimoto's autoimmune thyroiditisradiation damagethyroidectomyiodine deficiencyautosomal defects in hormone synthesisidiopathicSecondary hypothyroidism
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HypothyroidismMyxedema: Onset of hypothyroidism in the adultNamed for characteristic thickening of subcutaneous tissue caused by deposition of mucopolysaccharides Once thought to be due to increased mucus ("myx") formation
Cretinism:Onset in infancyUsually due to thyroid dysgenesisImpaired physical growthImpaired brain growth and myelinationMental retardation
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Adverse effectsNervousnessHypertensionVomiting and diarrheaIncreased sensitivity to heatImpaired reproductive functionCardiotoxicityIatrogenic hyperthyroidism Especially in the elderlyArrhythmiasShortness of breath
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Contraindications to T4 therapyUse with caution in presence of:Adrenal insufficiency: increases cortisol turnoverCoumarin anticoagulants: increases catabolism of clotting factorsDiabetes mellitus: increases insulin requirementStimulates gluconeogenesis and glycogenolysisCardiovascular disease: initiate therapy slowly, monitor closely because of effects on the heart
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Thionamides: Clinical usesGraves' hyperthyroidism:
100 to 600 mg propylthiouracil/day in divided doses or 10 to 40 mg methimazole /day as single doseReduce dose for maintenanceContinue for 6 months or longer, until remissionPropylthiouracil: also partially inhibits T4 T3 May be used when fast action is desiredMethimazole: longer duration of actionSuitable for once daily dosingPropylthiouracil indicated for hyperthyroidism during pregnancyUse minimum dose that controls symptoms
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Thionamides: Clinical usesFollowing radioiodine treatment:To achieve euthyroid status until effects of radiation are observedPrior to subtotal thyroidectomy:Euthyroid status improves response to surgical stress
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Thionamides: Adverse effectsSkin rashesAgranulocytosis (in 0.3 % of patients) -reversible upon discontinuationArthralgia and myalgiaHepatic abnormalitiesnecrosis (propylthiouracil)cholestatic jaundice (methimazole)
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Radioactive iodine (131I)Most common treatment in U.S.Radioactive T1/2: 8 daysRapidly and efficiently trapped by the thyroidDose is determined by preliminary uptake testAdjusted for complete or partial destruction of thyroid with no injury to adjacent tissueAdjunctive therapy:-adrenergic blocking agents (propanolol) orCa2+ channel antagonists (verapamil)For relief of symptoms (tachycardia, hypertension, arrhythmias) until euthyroid