M.Prasad NaiduMSc Medical Biochemistry,

Ph.D.Research Scholar

INTRODUCTIONMaster gland / master of endocrine orchestraReddish / GrayOval10 mmBrain – Optic chiasma – base of the brainExtension – Hypothalamus0.6 – 0.7 gm Males0.5 – 0.6 gm Females

INTRODUCTION3 Lobes1. an anterior / pars distalis /

adenohypophysisAn intermediate / pars intermediaA posterior / pars nervosa / neurohypophysis

Pars distalis / adenohypophysis70% Originates from an embryonic invagination of

pharyngeal epithelium – Rathke’s pouch2 types of hormones1. Tropic / Trophic / Trophin hormones2. Growth Hormone

Trophic HormonesSecreted by one gland and controls the

activities of other endocrine glands., Viz1. TSH (Thyroid Stimulating Hormone)2. ACTH ( AdrenoCorticoTropicHormone)2. Gonadal Hormones (Sex Hormones)

TSHGlycoprotein30,000HexosamineStimulates Thyroid gland – ThyroxineHyperthyroidismRapidly ↑ every phase of T4 metabolismActivates thyroidal adenylcyclase↑ thyroid growth

TSH↑ general metabolic activities such as

glucose oxidation, O2 consumption, Synthesis of Phospho lipids Protein synthesis RNA synthesis* In adipose tissue - Lipolysis

Regulation1. TRFHypothalamusTripeptide ( Pyro glu – His – Pro CONH2)Highly specific – acts only on TSH secreting

cells2. Low T4 ↑ TSH ; High T4 ↓ TSH

ACTH / CORTICOTROPHINStimulates A. Cortex hormonesPP chain – 39 aminoacids4500 mol.wt1-23 – biological activity15-18 most potent1-24 & 34-39 no change

FunctionsMost Imp phy. regulator – A. Cortex except

aldosteroneHypertrophy with temporary reduction in A.

lipids & vit C↑ blood flow to A. glands↑ formation of c- AMP in A. CortexIn liver , retards metabolic degradation &

conjugation of CorticosteroidsThus ↑ half life & activity of hormones

FunctionsIn AT, ↑ lipolysis↑ utilization of Glu- ↓ blood glu conc↑ glycogenesis by promoting insulin secretion↑ excretion of N,K,P & Uric acidRetards the syn.of Urea↑ GluconeogenesisRetards protein syn in all tissues except liver↑ melanocyte stimulating activity darkening of

skinOver secreting Cushing’s syndrome

Regulation1. CRF – HypothalamusCRF is liberated under the influence of non

specific stress, cold, emotional stress, drugs, toxic agents, Epinephrin, Oesrogens, T4, hGF, ADH etc

2. Conc. Of glucocorticoids

Gonadotrophins / gonadotrophic hormonesDevelopment & functioning of gonadsFunction and maturation of Testis & OvariesDamage to Hypothalamus ↓ secretion of

gonadotrophinsIf this occurs b4 to puberty simultaneous

over eating Since effect on feeding centre of hypothalamusObesity – adiposogenital syndrome / Frohlich’s

syndrome / hypothalamic eunuchism3 types of gonodotrophins

FSHGlycoproteinGal, Man, Hex-NH2, sialic acid, fucose, uronic acid30,000Males ↑ Spermatogenesis and production of

androgensFemales Growth & maturation & expulsion of ova

& controls the internal secretions of ovariesFSH is active during M.CycleFSH induces growth of graafian follicles ↑ wt of ovaryREGULATION:FSH- RF ( Hypothalamus)

LH (ICSH)Peptide hormone26000 lacks Trp but high Cys & Pro1 LH 10 Glu-NH2 + 3 Gal–NH2

In females ripening & rupturing of ovarian follicles which later transform into Corpus lutea

Induces the development of interstitial cells of both testis & ovaries

Regulation: LH – RF ( Hypo ) deca peptide

LTHThe most versatile of all adenohypophyseal

hormones1st ante. pituitary hor obtained in pure formPeptide – 198 aa – 235003 s-s bonds4 ; 4-14,58-173,190-198No carbohydrate ( unlike FSH & LH)Thermolabile – destroyed by Tryptic dig.In association with estrogens ↑ growth of

M.glands & induces secretion of milk

LTH↑ Glucose uptake ↑ lipogenesisAlong with androgens causes development of 20 male sex

characteristicPL is credited with performing > 80 functions Jack-of-all-trades5 major categories1. Reproduction 2. Osmoregulation 3. Growth4. integument 5. Synergic effect with steroid hormones↑ Leydig tissue , therefore male accessory organAppears sharply after pregnancy in UrineRegulation: PRF ( Hypothalamus)

Growth hormone

Growth Hormone / SomatotrophinSTH / GH is PP – 190 27000Phe---------------PhePI = 4.92 S-S bonds ; 53 - 164; 181 - 188

Functions↑ Overall protein synthesis↑ Erythropoiesis & growth of liver, intestine kidney↑ chondrogenesis, ossification & Osteogenesis

Skeletal growthCM:- 1. Hyperglycemia

2. In muscles – antagonises – insulin 3. diabetogenic effect ( degerative changes in

islets of langarhans & adrenal enlargement) 4. ↑ blood glu by promoting the secretion

of glucagon

FunctionsLipid Metabolism:- Lipolysis ↑ ↑ FA Oxidation ↑

ketogenesis & ↓RQ↑ intestinal absorption + excretion of Ca2+

Helps in retaining Na+, K+, Mg2+,Po43-,Cl-

GH binds to membrane receptors for prolactin and ↑ growth + enlargement of M. glands

Regulation1. GH.RF / SRF ( Hypothalamus)2. Blood sugar ↑ Glu ↑ GH secretion & vice versa3. EEE ↑ Exercise, Excitement & Exposure to

cold4. Arg ↑ GH in plasmaPituitary Diabetes:- Glu utilization is

moderately depressed ( In DM No utilization of glucose)

No other side effects

PARS INTERMEDIAAbsent in certain mammals – whale, Indian

elephantSecretes melanocyte ( melanophore ) MSH2 typesα- MSH (acylated------------13 Val-CONH2)β- MSH (Asp---------------18 Asp) (Humans 22aa)α- MSH – terminal groups are blockedβ- MSH - both the end groups are freeα- MSH > β- MSH ( biologic activity)

Functions↑ deposition of melanin by melanocytes of

human skin darkening of skin

Regulation:-

Inhibitors: Cortisone, OH- Cortisone, Adrenalin, Nor-adrenalin

Posterior pituitary / Neurohypophysis3 divisions

1. the pars nervosa2. neural stalk3. the median eminence

HistologyPosterior pituitary does not secrete hormones

but stores the hormonesThe cells of PP are of neural typeConsists of un myelinated nerve fibers and

pituicytes ( glial cells ) These cells possess brown pigment granules

Pituicytes act as supporting cells and do not secrete any hormone

The PP also blood vessels , hyaline bodies, neurological cells, mast cells etc.,

Regulation and SecretionPP is regulated by nerve fibers coming from the

hypothalamusPP does not secrete – therefore hormones are

synthesized in hypothalamus & transported to PP ( stored in nerve endings)

When ever impulses from hypothalamus reach PP, these hormones are released from the nerve endings

Hormones are PP Oxytocin & Vasopressin

Oxytocin( Oxy G = Quick ; tokos G = birth) (Pitocin)Nanopeptide

FUNCTIONS:

Ejection of milk ↑ contraction of smooth muscles- uterus,Also contraction of intestine, U.bladder, &

ducts of M. glandsM. glands are lined by myoepithelial cells

Milk ejection reflex / milk let down reflex (neuroendocrine reflex)Many touch receptors around the nipple When the infant suckles the nipple Touch receptors stimulated Impulses are discharged nerve fibersPara ventricular nucleus ( Hypothal) Oxytocin Blood ( Oxytocin) Reaches Mammary gland Contraction of myoepithelial cells Ejection of milk

Vasopressin / ADHProduces constriction of blood vesselsSecreted by supra optic nucleus of hypothalSmall quantity by para ventricular nucleus of

hypothalThen transported via nerve fibers PP

Functions1. Regulation of H2O by acting on kidneys water reabsorption from DCT , C. ductIn the absence of ADH reabsorption of water does not

– dil urine excreted – excess water via Urine – Diabetes insipidus

2. Vasopressor effect of ADH:-Constriction of arteriesHowever the amt of ADH req to cause vasopressor effect

is very much more than the amt required to cause antidiuresis

Regulation1. Volume of body fluid2. Osmolality of ECFPotent Stimulators: 1. ↓ in the vol of ECF2. ↑ in osmolar conc in ECFADH secretion ↑ emotional + physical stress,

Ele stimulation, Ach, Nicotine, Morphin