Home >Documents >Nomad: Thyroid Physiology

Nomad: Thyroid Physiology

Date post:14-Oct-2014
Category:
View:1,760 times
Download:3 times
Share this document with a friend
Description:
Why is the Thyroid gland so named? What is its special characteristic? How are it's hormones synthesized? What are their functions? What happens when these hormones are deficient in the fetal stage and in adulthood? What if they become too high in concentration? For answers, read on.
Transcript:

THYROID GLAND IBy Dr. M. Anthony David, MD Professor of Physiology02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA 1

THE THYROID GLAND

Thyreos Greek for Shield. Morphology:

Largest Endocrine gland: 15 25 Gms in weight. Has two lobes connected by an Isthmus Is richly vascular; 4 -6ml/g/min Has sympathetic innervationNOMAD:ENDOPHYSIOL: THYROID PARA 2

Anatomy:

02/09/08

T H Y R O I D G L A N D

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

3

THYROID GLAND

EMBRYOLOGY:Begins development in the 4thwk of IUL Hormones secreted from the 12th week. Fetal Thyroid Hormones useful for: Normal

Fetal Bone maturation. Normal development of the CNS.02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA 4

THYROID GLAND HISTOLOGY:3

02/09/08

Million spherical follicles 50 - 500 in diameter Each follicle has clear viscid protein colloid called Thyroglobulin The Parafollicular C cells secrete (Thyro) Calcitonin.NOMAD:ENDOPHYSIOL: THYROID PARA

5

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

6

BIOSYNTHESIS OF THYROID HORMONESIODINE UPTAKE & TRAPPING IODINATION & COUPLING

Tyrosine + Iodine = Mono Iodo Tyrosine (MIT) MIT + MIT = Di Iodo Tyrosine (DIT) MIT + DIT = Tri Iodo Tyrosine T 3

DIT + DIT = Tetra Iodo Thyronine 02/09/08 (T4) NOMAD:ENDOPHYSIOL: THYROID PARA

7

I O D I N A T I O N & C O U P L I N G02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA 8

BIOSYNTHESIS OF THYROID HORMONES COUPLED

HORMONES COMBINE WITH THYROGLOBULIN, COLLOID. ARE FREED BY PROTEOLYSIS THE FREE THYROID HORMONES ARE THEN RELEASED INTO THE BLOOD02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA

9

TRANSPORT OF THYROID HORMONES

60% : THYROXIN BINDING GLOBULIN (TBG) 30% : THYROXIN BINDING PRE ALBUMIN (TBPA) 10% : ALBUMIN

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

10

EFFECTS OF THYROID HORMONES: Metabolic

CALORIGENESIS:Heat Production.

REGULATION:

Transport:Ions Water

Intermediary metabolisms:CHO Fats Proteins

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

11

EFFECTS OF THYROID HORMONES: Developmental REGULATION: Growth

in Homeotherms Metamorphosis in Poikilotherms. CONTROL: Protein 02/09/08

Synthesis.

NOMAD:ENDOPHYSIOL: THYROID PARA

12

CALORIGENESIS: Heat Production

How? By increasing Oxygen consumption in:

Heart Gastric Mucosa Smooth Muscles Kidneys Liver Skeletal Muscles.NOMAD:ENDOPHYSIOL: THYROID PARA 13

02/09/08

CALORIGENESIS: Heat Production

No response to Thyroxine in

T: Testes U: Uterus L: Lymph nodes S: Spleen A: Anterior Pituitary Tachycardia Sensitivity to Adrenal Lipolysis.NOMAD:ENDOPHYSIOL: THYROID PARA 14

Results:

02/09/08

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON THE HEART: POSITIVE CHRONO & IONOTROPIC EFFECT

No & affinity of adrenergic receptors Response to Catecholamines Proportion of 02/09/08 alpha Myosin heavy NOMAD:ENDOPHYSIOL: THYROID PARA

15

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON THE ADIPOSE TISSUE:

Thyroid hormones are catabolic. They cause Lipolysis. Catabolic Protein lysis.16

ON MUSCLES:

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON THE BONE:

Developmental effect: Normal growth & development.

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

17

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON THE NERVOUS SYSTEM:

DEVELOPMENTAL Promotes normal development

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

18

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON THE GUT:

METABOLIC EFFECT: CHO Absorption

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

19

THYROID HORMONES: PHYSIOLOGIC ACTIONS

ON LIPOPROTEINS:

METABOLIC EFFECT: LDL Receptor formation.

OTHER: CALORIGENESIS BMR:

Oxygen consumption in most tissues except Testes, Uterus, Lymph nodes, Spleen & Anterior Pituitary.NOMAD:ENDOPHYSIOL: THYROID PARA 20

02/09/08

THYROID HORMONES: METABOLIC EFFECTS

CARBOHYDRATES:

GLUCOSE PRODUCTION BY: Glycogenolysis Gluconeogenesis Hunger - Intake of food

ANTI INSULIN EFFECT: Catabolism of Insulin Secretion of Insulin

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

21

THYROID HORMONES: METABOLIC EFFECTS

LIPIDS:

Synthesis Lysis Hypothyroidism:

S. Cholesterol: 400 700 mg% S. Cholesterol: 100 150 mg%

Hyperthyroidism:

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

22

THYROID HORMONES: METABOLIC EFFECTS

PROTEINS:

Anabolism Converts Carotene to Vit A & Retinene. Metabolism disturbed in Hypothyroidism Causes Myxedema: Dry Coarse Puffy skin.NOMAD:ENDOPHYSIOL: THYROID PARA 23

VITAMINS:

MUCOPOLYSACCARIDES:

02/09/08

THYROID HORMONES: METABOLIC EFFECTS

BMR:Increases by 60 to 100 % How? By increasing the size and number of Mitochondria.

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

24

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

25

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

26

THYROID HORMONES: A NEGATIVE FEEDBACK REGULATIONHYPOTHALAMUS

TRH ANT PIT TSH

STIMULATING INHIBITORY

TARGET TISSUES02/09/08

T3 & T4 THYROID GLANDNOMAD:ENDOPHYSIOL: THYROID PARA 27

APPLIED ASPECTS

EUTHYROIDISM: Normal thyroid status HYPOTHYROIDISM:

In infancy: Cretinism (Thyroid dwarfism) In adults: Myxedema, Hypothyroidism ThyrotoxicosisNOMAD:ENDOPHYSIOL: THYROID PARA 28

HYPERTHYROIDISM:

02/09/08

HYPOTHYROIDISM

CHILDREN: CRETINISM:

Congenital Hypothyroidism Dwarfism Mentally Subnormal: MR Enlarged, Protruding tongue Pot bellies.

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

29

C R E T I N I S M02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA

P R O T R U D I N G

T O N G U E30

HYPOTHYROIDISM: ADULTS

MYXEDEMA: CAUSES:

Primary: Thyroid diseases Secondary: Pituitary or Hypothalamic cause.

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

31

MYXEDEMA: CLINICAL FEATURES

Low BMR: - 40 Coarse & Sparse Hair Dry & Yellow skin ( Carotenemia) Poor Cold toleration Voice: Husky & slowNOMAD:ENDOPHYSIOL: THYROID PARA 32

02/09/08

MYXEDEMA: CLINICAL FEATURES

Plasma Cholesterol Slow mentation Poor memory Severe mental symptoms: Myxedema madness DepressionNOMAD:ENDOPHYSIOL: THYROID PARA 33

02/09/08

HYPOTHYROIDISM: TREATMENTVery effective treatment available. Replacement of the deficient Tab Eltroxin Thyroxine by Oral One tablet tablets. a day Brand name Life long Eltroxin This causes all the clinical features 02/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA to disappear.

34

HYPERTHYROIDISM

Also called Thyrotoxicosis Hyperphagia + Weight loss Heat Intolerance Pulse Pressure Sleeping Pulse Rate >90/minNOMAD:ENDOPHYSIOL: THYROID PARA 35

02/09/08

HYPERTHYROIDISMNervousness, Anxiety Fine Tremor: Paper test Warm, soft skin Sweating BMR: +10 to +10002/09/08 NOMAD:ENDOPHYSIOL: THYROID PARA 36

HYPERTHYROIDISM: GRAVES DISEASE

EXOPHTHALMIC GOITRE: Exophthalmos: Protruding eyeballs Is an autoimmune disorder Can be also Hashimotos ThyroiditisNOMAD:ENDOPHYSIOL: THYROID PARA 37

02/09/08

TREATMENT OF HYPERTHYROIDISM

Antithyroid drugs: Most drugs interfere with Iodide trapping. Others block iodisation of Tyrosine. Examples: Perchlorates Thiocyanates Decrease Goitrogen consumption:NOMAD:ENDOPHYSIOL: THYROID PARA 38

02/09/08

GOITROGENS

Goitrogens: Goitrin & Progoitrin seen in: Cabbage Rutabagas & TurnipsNOMAD:ENDOPHYSIOL: THYROID PARA 39

02/09/08

02/09/08

NOMAD:ENDOPHYSIOL: THYROID PARA

40

Popular Tags:

Click here to load reader

Embed Size (px)
Recommended