Dr. dr. H. Busjra M. Nur, MScFKK UMJ

HormonesHormones are chemical signals that are used for communication between cells.

Chemically, hormones are rather diverse group of substances. They are derived from metabolism of amino acids, polypeptide or cholesterol (steroid).

HormonesBinding of a hormone to its receptor

and activation of that receptor is the initial in producing a hormone effect.

Some hormones act via second mesengers to alter activity of reexisting proteins in target cells.

Other hormones act by altering gene expression in target cells to change the amount of a few key proteins.

Targets Each hormone binds to a specific tissue / organ target tissue / organ

Hormone Receptors Membrane receptorsIntra cellular receptors second messenger

The general mechanism of action of hormones with membrane receptor

Illustration of coupling of membrane receptors to adenylate cyclase by the Gs and Gi proteins.

Mechanism of action of hormones with intracellular receptors, effects on gene expression, cell function might be altered.

Mechanism of action of aldosterone to increase sodium transport across kidney tubule cells

Basic mechanisms of neural (a), endocrine (b) and neuroendocrine (c)

Controle of Hormone SecretionNegative FeedbackBiorhythmsBy Central Nervous System

Endocrine glandsHypothalamusPituitary glandPineal glandThyroid glandParathyroid

glands

Thymus glandAdrenal glandsPancreasTestes (male)Ovaries (female)Others

The Pituitary HormonesThe pituitary consist of two main lobes

(anterior and posterior)The hypothalamus serves to regulate

secretion from both lobesThe anterior pituitary secretes six different

hormone into the general circulation

The Pituitary HormonesThe posterior pituitary is a neuroendocrine

gland; it secretes two hormones and contains the terminals of neuroendocrine cells, in the hypothalamus

GH, affects skeletal growth, protein and carbohydrates metabolism

TSH, regulates thyroid hormone production. Thyroid hormone regulate metabolism in most tissues in the body

Neural and vascular connections between the hypothalamus and the anterior and posterior lobes of pituitary.

Growth Hormone (GH)= somatotropin= somatotropic hormone (STH)Growth of skeletal muscle and long bone

Metabolic effect (protein, fats, glucose)

Growth Hormone

Hypersecretes –- gigantism -- acromegaly

Defisiency (childhood) – pituitary dwarfism

Normal hand and acromegaly

Prolactin (PRL)= lactogenic hormonePromotes milk production in woman

The Thyroid GlandSecretes /day - T4 (thyroxine): 80 μg - T3 (triiodothyronine) 4 μg

Iodine Deficency T3-T4 production T3-T4 plasma level TSH secretion thyroid gland stimulation goiter

Thyroxine Defisiency Infant : Cretinism – fail to develop both physically and mentally

Adult : hypothyroidsm myxedema – metabolic state , low energy, low body temperature, heart rate , constipation

The Adrenal GlandsConsist of cortex and medulla Adrenal cortex produce steroid

hormones, predominantly cortisol and aldosterone.

Cortisol metabolism release of stored fuels.

Aldosterone kidneys sodium and potassium balance in the body.

The Adrenal Glands

The adrenal medulla as part of the sympathetic nervous system epinephrine.

Epinephrine cardiovascular, pulmonary systems a variety of metabolic

processesThe net effect of cortisol and epinephrine

increase the body’s ability to effectively respond to stress.

The Endocrine PancreasProduces insulin and glucagon, major roles in

regulating fuel homeostasis in both the fed and fasted states

Insulin is secreted primarily in response to an increased blood glucose level. Glucagon is secreted in response to a decreased v\blood glucose level.

Insulin directs the storage of excess nutrients in the form of glycogen, triacylglycerols, and protein. The major tissue targets of insulin are liver, muscle and adipose tissue.

The Endocrine PancreasGlucagon directs the movement of stored

nutrients into the blood stream. Liver is the primary physiological target of glucagon.

In the fed stated, the actions of insulin predominate in tissues, and nutrients are stored. In the fasted state, the actions of glucagon predominate, and stored nutrients are mobilized.

Diabetes mellitus occurs when there is a deficiency in insulin action as a result of either an impairment in insulin secretion or an impairment in its target tissues.

Pineal gland and Circadian rhythmsSecretes hormone melatoninMelatonin keep the body’s inherent circadian

rhythms in synchrony with the light-dark cycle.

Melatonin Circadian timekeepingInduce natural sleepAntioxidant Slow aging processEnhance immunity

Hormone : Amino acid

ThyroxineEpinephrineMelatonin

Hormone: Polypeptides

TRH (thyrotropin releasing hormone)

ACTH (adrenocorticotropic hormone)

PTH (parathyroid hormone)GH (growth hormone)FSH (follicle-stimulating hormone)

Hormone: Steroids

GlucocorticoidsMineralocorticoidsAndrogensEstrogensProgestins

ReferencesHerlihy,B and Maebius NK. The Human Body

in Health and IllnessGanong WF. Review of medical physiology.

22th ed.Rhoades R, Pflanzer R. Human Physiology. 4th

ed. Sherwood L. Human Physiology, from cells to

system. 5 th ed.