ENDOCRINOLOGY Prof/ Faten & Dr . Taj

1. ENDOCRINOLOGY Prof/Faten & Dr. Taj

2. ENDOCRINOLOGY: It is study of functions of HORMONES, that are released from glands called endocrine glands distributed throughout the body. HORMONES: Are secretions of ductless glands that are directly released into the blood stream. They can act on cells in the vicinity or on distant target cells.

3. Response vs. distance traveled • Endocrine action: the hormone is distributed in blood and binds to distant target cells. • Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood. • Autocrine action: the hormone acts on the same cell that produced it.

4. Endocrine glands: Pituitary Thyroid Parathyroid AdrenalPancreasOvaries Teste

5. Classification of hormones Hormones are categorized into three major structural groups. • Peptides and proteins: largest group containing all hormones from the Hypothalamus, Pituitary, Pancreas, Parathyroid, Thyroid “C” cells etc.. • Amino acid derivatives: (Tyrosine). Hormones include Catacholamines (Epinephrine and Nor-epinephrine) and Thyroid hormones (T3 & T4) • Steroids: Hormones include those from Adrenal Cortex, Gonads and Placenta.

6. A cell is a target because is has a specific receptor for the hormone Most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called TARGET CELLS. A target cell responds to a hormone because it bears RECEPTORS for the hormone.Receptor are highly specific to their binding substances/hormones.

7. Receptors • Receptors for specific hormones are present either IN or ON the cell depending upon the permeability of the hormone. • If the hormone can gain entry into the cell i.e. (it is permeable) then its receptor is either in the cytoplasm or the nucleus of the cell • If the hormone is not permeable then its receptor is found on the cell membrane.

8. Hormone + Receptor

9. Mechanisms of Action of Hormones 1. PEPTIDE HORMONES: Usually channel changes or activation of 2nd messenger system to alter activity of pre-existing proteins that produce the effect.

10. Mechanisms of Action of Hormones 2 2. AMINES • Catacholamines: Activation of second messenger system to alter activity of pre-existing proteins that produce the effect. • Thyroid Hormones (T3, T4): Activation of specific genes to synthesize new proteins that produce the effect. • STEROIDS: Activation of specific genes to synthesize new proteins that produce the affect.

12. HORMONES OF THE BODY:-1- Anterior pituitary hormones2-Posterior pituitary hormones3-Adrenal cortex hormones ( cortisol-aldosterone) 4-Thyroid gland hormones (thyroxine)5-Hormones of the islets of langerhans in pancreas(insulin-glucagon) 6-Hormones of the ovaries (estrogen-progesterone7-Hormones of the testes(testosterone) 8-Parathyroid gland (parathormone) 9- Placental hormones (estrogen-progesterone-human chorionic gonadotropin

13. Hypothalamus CONNECTION TO PITUITARY Neuronal to POSTERIOR PITUITARY Endocrine to ANTERIOR PITUITARY

14. Hypothalamus and the Pituitary gland Supraoptic Nucleus (ADH) Para ventricular Nucleus (Oxytocin) (ADH & Oxytocin)

15. The pituitary gland connected to hypothalamus by the pituitary stalk. Consists of 2 parts a- the anterior pituitary b- posterior pituitary . Hormones produced by anterior pituitary are :- 1-TSH (thyroid stimulating .h) 2- ACTH (adrenocorticotrophic.h) 3-FSH (follicle stimulating.h) 4- LH (leutinizing .h) 5-GH (growth.h) 6-PROLACTIN

16. 1-Thyroid Stimulating Hormone (TSH) TSH stimulates the thyroid gland to secrete its hormone thyroxin 2-ACTH — the adrenocorticotropic hormone Release of corticosteroids & glucocorticoids from adrenal cortex 3- L.H:- stimulates ovulation in female Stimulates testosterone secretion in male 4-FSH:- stimulates ovum maturation in female Stimulates spermatogenesis( sperms formation ) in male 1-Prolactin (PRL):-from the anterior lobe of the pituitary gland : Stimulate milk synthesis

18. Anterior Pituitary(Adenohypophysis) Hormones

19. Posterior Pituitary (Neurohypophysis) Hormones • Manufactured in Hypothalamus, released from Post. Pituitary. • Oxytocin • Target = smooth muscles, Uterus and Breast. • Function = labor , delivery, milk ejection (let down). • ADH (Vasopressin) • Target = kidneys • Function = water reabsorption

20. Oxytocin a-contracts the alveoli of the breast, helping to deliver milk from the glands of the breast to the nipples during suckling (milk ejection-reflex) b-Contracts the uterus, thus helping the delivery of the baby at the end of gestation • ADH( vasopressin) • -controls the rate of water excretion into urineand in this way helps to control the concentration of water in the body fluids & is a vasoconstrictor

22. Why is the Hypothalamus so Important? • It secretes regulatory hormones which are either • Releasing hormones • or • Inhibitory hormones • They "Directs" the pituitary and regulate its secretions

23. Hypothalamic - Pituitary Axis

24. STIMULUS Hypothalamus (Releasing Hormone &Inhibiting Hormone) Pituitary Stimulating Hormone Gland Hormone Target

25. Hypothalamic Hormones • Release Inhibiting Hormones • Somatostatin(growth hormone-inhibiting hormone) (GHIH) • Prolactin inhibiting hormone-PIH • Releasing Hormones • Thyrotropin releasing hormone-TRH • Growth hormone releasing hormone-GHRH • -Gonadotropin releasing hormones –GnRH • - Corticotropin releasing hormones -CRH

26. Control of Endocrine Function • Positive • Negative Feedback mechanisms • Self-regulating system

27. A. Positive Feedback • Not common • Classic example: Action of OXYTOCIN on uterine muscle during birth.

28. B. Negative Feedback • Most common control mechanism • Increasing levels of the hormone or its required effect causes inhibition at the pituitary/ Hypothalamic levels returning the hormone levels back to normal.