Endocrinology

Endocrinology  Communication

and control  Made possible by chemical mediators  “Hormones” – Chemical substances – Active in small quantities (10-7 to 10-10M) – Affect function of distant, nearby or source cell

Metabolism  Biochemical

control mechanisms  Gene expression  Chemical mediator synthesis and release  How cells modify, transform and degrade  How chemical mediators mediate their action  Storage and mobilization of energy

Classification of Hormones According to structure  Amino

acid derivatives

– Tyrosine: NE,E,DA, T3, T4

 Peptides/proteins/glycoproteins – TRH, GH, LH

 Steroids/cholesterol

derivatives

– Glucocorticoids, mineralocorticoids, sex

steroids, vitamin D

Classification of Hormones According to function  Reproduction – Testosterone, estrogen, prolactin, LH, FSH

 Growth

and development

– GH, estrogen, testosterone

 Homeostasis – ADH, PTH

 Energy

availability

– Insulin, glucagon, T3, T4

Types of cell-to-cell interaction

Hormone action  Target

cells – cells that eventually receive the hormone in the circulation  Receptor – specialized structure that will bind a particular hormone – Recognition domain – Coupling domain

Regulation of Hormone Secretion Negative

feedback – most common, acts to limit the excursions in output of each partner in the pair Positive feedback – acts to amplify the initial biological effect of the hormone

Physiology of the Hypothalamus and Pituitary Gland

Hypophysis Adenohypophysis – Somatotropes, corticotropes, thyrotropes,

gonadotropes, lactotropes – Null cells Neurohypophysis Pars

intermedia

Anterior Pituitary Hormones  Growth

Hormone (somatotropin)  Adrenocorticotropic Hormone (corticotropin)  Thyroid Stimulating Hormone (thyrotropin)  Prolactin  Follicle Stimulating Hormone (FSH)  Luteinizing Hormone (LH)

GH Secretion Stimulated by:  Hypoglycemia  Amino

acids  Onset of deep sleep  Dopamine  Thyroid hormone  Cortisol  estrogen

GH Secretion Inhibited by:  Hypoglycemia  FFA  Progesterone  Cortisol  Beta

adrenergic agonists

Prolactin  Promotes

mammary gland development together with estrogen, progesterone, glucocorticoids, insulin  Lactogenesis and milk production

Prolactin Secretion Stimulated by:       

Pregnancy Estrogen Nursing Sleep Stress TRH Dopaminergic antagonists

Inhibited by:  Dopamine  Dopaminergic

agonists  Prolactin  GABA

ADH Secretion Stimulated by:

Inhibited by:

 Osmolality

 Osmolality

increase  Volume decrease  Pressure decrease  Pain  Nausea & vomiting  Stress  hypoglycemia

decrease  Volume increase  Temperature decrease  Ethanol  cortisol

Physiology of the Pancreatic Islets

Insulin Secretion Stimulated by:

Inhibited by:

 Glucose



 Amino



acids  Intestinal hormones  Ketoacids  Acetylcholine  Glucagon  Cyclic AMP

   

Somatostatin Alpha derenergic stimulators Beta adrenergic blockers Diazoxide Thiazide diuretics phenytoin

Glucagon Secretion Stimulated by:

Inhibited by:

 Amino

 Glucose

acids  CCK, gastrin  Cortisol  Exercise  Infections  Other stresses

 Somatostatin  Secretin  FFA  Ketones  Insulin

Somatostatin  Decreases

glucagon and insulin secretion  Decreases motility of stomach, duodenum and gall bladder  Decreases secretion and absorption in GIT  Stimulated by all factors related to foos, I.e.:blood glucose, AA, FFA, GI hormones

Physiology of the Thyroid Gland

oxidation trapping

organification

•Peripheral conversion of T4 to T3 in liver, muscles, kidneys.

coupling

TSH Promotes

growth of thyroid gland Stimulates all aspects of function – Glandular uptake of iodine – Organification – Completion of thyroid hormone synthesis – Release of thyroid gland products

Control of TSH secretion Stimulated by: TRH estrogen

Inhibited by: T3, T4 Somatostatin CCK Glucocorticoids Androgens