LOCATED: BELOW LARYNX WEIGHT: 15-20 GM TWO HORMONE: THYROXINE (T4) AND TRI-IODOTHYRONINE (T3) CONTROL: TSH FROM ANTERIOR PITUITARY GLAND CALCITONIN: CALCIUM METABOLISM

1. THYROID HORMONES
LOCATED: BELOW LARYNX
WEIGHT: 15-20 GM
TWO HORMONE:
THYROXINE (T4) AND TRI-
IODOTHYRONINE (T3)
CONTROL: TSH FROM
ANTERIOR PITUITARY
GLAND
CALCITONIN: CALCIUM
METABOLISM

2. SYNTHESIS OF THYROID HORMONES
COMPOSED: FOLLICLES FILLED WITH COLLOID
MAJOR CONSTITUENT: THYROGLOBULIN
IODIDE ABORBTION FROM GIT, COMBINE WITH TYROSINE
THYROGLOBULIN: 30 THYOXINE AND FEW TRI-IODOTHYRONINE
RELEASE OF THROXINE AND TRI-IODOTHYRONINE
• SURFACE OF THYROID CELLS SEND OUT PSEUDOPOD EXTENSIONS,
CLOSE AROUND COLLOID, FORM PINOCYTIC VESICLES
• PROTEASES IN CYTOPLASM, FUSE WITH VESICLES, DIGEST THYROGLO-
BULIN AND RELEASE THYROXINE AND TRI-IODOTHYRONINE IN FREE
FORM, 93%, THYOXINE AND 7% TRI-IODOTHYRONINE
• COMBINE WITH PLASMA PROTEIN , SLOWLY USED AT TARGET CELLS
FOR DAYS AND WEEKS

3. PHYSIOLOGICAL FUNCTIONS OF THYROID HORMONES
THROID HORMONES INCREASE TRANSCRIPTION OF LARGE NUMBERS
OF GENES
IN ALL CELLS OF BODY, INCREASE NUMBER OF PROTEIN (ENZYMES,
STRUCTURAL PROTEIN, TRANSPORT PROTEIN) AND INCREASE
FUNCTIONAL ACTIVITY THROUGHOUT THE BODY
THYROID HORMONES ACTIVATE NUCLEAR RECEPTORS
BIND WITH DNA, INITIATE TRANSCRIPTION, mRNA FORMED, RNA
TRANSLATION NEW INTRACELLULAR PROTEIN FORMED
THYROID HORMONES INCREASE CELLULAR METABOLIC ACTIVITY
INCREASE METABOLIC ACTIVITY, RATE OF UTILIZATION OF FOOD FOR
ENERGY, RATE OF PROTEIN SYNTHESIS AND CATABOLISM INCREASED,

4. THYROID HORMONES INCREASE NUMBER AND ACTIVITY OF MITOCHONDRIA
INCREASE RATE OF FORMATION OF ATP, INCREASE ACTIVITY OF CELL
THROID HORMONE INCREASE ACTIVE TRANSPORT OF IONS THROUGH
CELL MEMBRANES
INCREASE ACTIVITY OF ENZYMR NaK ATPase, TRANSPORT OF IONS,
ENERGY USES AND INCREASE AMOUNT OF HEAT IN BODY
EFFECT OF THYROID HORMONE ON GROWTH
HYPOTHYROIDISM: RATE OF GROWTH RETARDED,IN
HYPERTHYROIDISM, EXCESSIVE GROWTH
STIMULATE CARBOHYDRATE METABOLISM
RAPID UPTAKE OF GLUCOSE BY CELLS, ENHANCED GLYCOLYSIS AND
GLUCONEOGENESIS, INCREASE RATE OF ABSORPTION FROM GIT,
INCREASE INSULIN SECRETION

5. STIMULATION OF FAT METABOLISM
LIPIDS METABOLIZED RAPIDLY, DECREASED FAT STORES OF BODY,
INCREASE FREE FATTY ACID CONC IN PLASMA, ACCELERATE OXIDATION
OF FATTYACIDS BY CELLS
INCREASE REQUIRMENT OF VITAMINS
INCREASE QUANTITY OF ENZYMES AND VITAMINS (ESSENTIAL PARTS OF
ENZYMES AND CO-ENZYMES), INCREASE NEED FOR VITAMINS
INCREASE BASAL METABOLIC RATE
INCREASE METABOLISM IN ALL CELLS, INCREASE BASAL METABOLIC RATE
60-100%
DECREASED BODY WEIGHT
INCREASE THYROID HORMONE-DECREASED BODY WEIGHT
INCREASE APPETITE, COUNTERBALANCE METABOLIC RATE

6. EFFECT OF THYROID HORMONES ON CARDIOVASCULAR SYSTEM
INCREASED BLOOD FLOW AND CARDIAC OUTPUT: INCREASE METABOLISM,
INCREASE UTILIZATION OF OXYGEN AND RELAESE OF METABOLIC END PRODUCT.
VASODILATION AND INCREASE BLOOD FLOW AND CARDIAC OUTPUT
INCREASED HEART RATE: INCREASE HEART RATE AND SENSITIVE SIGN TO
DETERMINE EXCESSIVE AND DIMINISHED THYROID HORMONE
INCREASED HEART STRENGTH: SLIGHT INCREASE IN THYROID
HORMONE:INCREASE STRENGTH, EXCESSIVE INCREASE ITHYROID HORMONE,
HEART MUSCLE STREGTH DEPREESED

7.  INCREASED RESPIRATION
INCREASE RATE AND DEPTH OF RESPIRATION
INCREASED GASTROINTESTINAL MOTILITY
INCREASES RATE OF SECRETION OF DIGESTIVE JUICES AND MOTILITY OF GIT
EXCITATORY EFFECTS ON CENTRAL NERVOUS SYSTEM
INCREASES CEREBRATION, EXTREME NERVOUSNESS, ANXIETY COMPLEXES,
EXTREME WORRY
MUSCLE FUNCTION
SLIGHT INCREASE THYROID HORMONE: VIGOR
EXCESS INCREASE OF THYROID: MUSCLE WEAK
LACK OF THYROID HORMONE: MUSCLES SLUGGISH, SLOWLY RELAX AFTER
CONTRACTION
FINE MUSCLE TREMOR: SIGN OF HYPERTHYROIDISM

8. EFFECT ON SLEEP
EXHAUSTING EFFECT OF THYROID ON MUSCULATURE, EXCITABILITY ON
SYNAPSES,IN HYPOTHYROIDISM, SLEEP LASTING 12-14 HOURS A DAY
EFFECT ON OTHER ENDOCRINE GLANDS
INCREASE RATE OF SECRETION OF ENDOCRINE GLANDS, INCREASE
GLUCOSE METABOLISM, INCREASE NEED OF INSULIN, INCREASE
METABOLIC ACTIVITIES IN BONE, INCREASE PARATHYROID HORMONE
EFFECT OF THYROID ON SEXUAL FUNCTION
HYPOTHYROIDISM: LOSS OF LIBIDO, HYPERTHYROIDISM: IMPOTENCE
LACK OF THYOID HORMONE: HEAVY AND PROLONG BLEEDING AND
IRREGULAR MENSTRUAL CYCLE
HYPERTHYROIDISM: INFREQUENT MENSTRUATION CAUSE AMENORRHEA

9. REGULATION OF THYROID HORMONE SECRETION
STIMULATING FACTORS
• TSH, AN ANTERIOR PITUITARY HORMONE, STIMULATED BY TRH BY
HYPOTHALAMUS, INCREASE SECRETION OF THYROID GLANDULAR
CELLS
• EXPOSURE OF COLD
• LOW METABOLIC RATE
INHIBITORY FACTORS
• EXCITEMENT AND ANXETY
• NEGATIVE FEEDBACK INHIBITION
• ANTITHYROID DRUGS OR LACK OF IODINE

10. HYPERTHYROIDISM
TOXIC GOITER, THYROTOXICOSIS, GRAVES' DISEASE
ANTIBODIES (THYROID STIMULATING IMMUNOGLOBULIN) FORMED
AGAINST TSH RECEPTOR IN THYROID GLAND, INDUCE CONTINUOUS
ACTIVATION OF cAMP SYSTEM OF CELLS, HIGH CONC OF THYROID
HORMONES AND SUPPRESS FEEDBACK BY ANTERIOR PITUITARY
SYMPTOMS: EXOPHTHALAMUS (PROTRUSION OF EYE BALL),
EXCITABILITY, INTOLERANCE TO HEAT, INCREASE SWEATING, WEIGHT
LOSS, VARYING DIARRHEA, MUSCLE WEAKNESS, NERVOUSNESS OR
OTHER PSHYCHIC DISORDERS,EXTREME FATIGUE, INABILITY TO SLEEP,
TREMOR OF HANDS

11. HYPOTHYROIDISM
CAUSE BY AUTOIMMUNITY AGAINST THYROID GLAND, ABSENT SECRETION
OF THYROID HORMONES
MYXEDEMA
LACK OF THYROID HORMONE FUNCTION
SYMPTOMS: BAGGINESS OF EYES, SWELLING OF
FACE, INCREASE BLOOD CHOLESTEROL
CRETINISM
HYPOTHYROIDISM DURING FETAL LIFE, FAILURE OF BODY GROWTH AND
MENTAL RETARDATION