introduction to endocrinology Flashcards
what is the definition of The Endocrine System ?
an integrated network of multiple organs of various embryologic origins, that release hormones ranging from small peptides to glycoproteins, which exert their effects in the vicinity or in distant target cells.
what is an Hormone ?
Chemical substance produced and secreted by one cell that travels through the blood to act on another cell.
what contains a Target organ ?
contains cells that express
specific receptors and show a biologic
response after hormone binding.
what is The components of the endocrine system ?
Endocrine glands
Hormones
Hormone transport pathways
Hormone receptors
how works Endocrine glands ?
the classic endocrine
glands are ductless and secret their chemical
products (hormones) into the interstitial space
and from there into the circulation; they are
not anatomically connected and are scattered
throughout the body.
where is located the Hypothalamus ?
Location: Diencephalon,
integrated part of the
nervous system
what is the role of hypothalamus ?
Releasing and inhibiting
hormones;
ADH, oxytocin.
WHAT ARE THE TWO PARTS OF The Pituitary Gland (Hypophysis) ?
Two parts:
Anterior pituitary gland
(adenohypophysis)
Posterior pituitary gland
(neurohypophysis)
Thyroid gland localisation ? WEIGHT ? CONSIST OF WHAT ? WHAT MAY BE PRESENT ?
located in the anterior neck in
front of the trachea.
weighs 10-25g;
consists of two lobes,
connected by an isthmus.
A pyramidal lobe may be
present, arising from the upper
isthmus
Parathyroid glands CHARACTERISTICS ?
Usually four;
rice grain size;
located at the top and bottom of
posterior faces of the thyroid
lobes;
May be up to 8, located in the
upper mediastinum
The Adrenal Glands CHARACTERISTICS ?
Located above the kidneys, small,
averaging 1-1.5 cm in lengh.
They are made of 2 different parts :
the adrenal cortex
the adrenal medulla.
The Gonads THE TYPES ? AND CHARACTERISTICS ?
Ovaries
oval-shaped glands located asides of the uterus.
Secrete both estrogen and progesterone;
Release ovules
Testes / testicles:
produce spermatozoa
Secrete testosterone
Classification of hormones
According to their chemical structure ?
Protein or peptide hormones
Steroid hormones
Amino acid- derived hormones
Eicosanoids (derived from polyunsaturated
fatty acids)
Classification of hormones
According to their properties ?
Hydrophilic hormones- the majority of
amines, peptides and protein hormones. They
bind to membrane receptors.
Lipophilic hormones: steroids and thyroid
hormones. They bind to the intracellular
(nuclear) receptors.
Hypothalamic hormones
Hypophysiotropic neurohormones TYPES ? CHARACTERISTICS ?
GHRH (growth hormone-releasing hormone) -stimulates the GH (growth hormone)
secretion.
TRH (thyrotropin-releasing hormone) has stimulatory effect on TSH and PRL (prolactin)
secretion
GnRH (gonadotropin-releasing hormone) - controls the secretion of both LH and FSH.
Dopamine - the main inhibitor of PRL (prolactine)
CRH (corticotropin-releasing factor) that stimulates the secretion of ACTH and other
products of its precursor molecule.
Somatostatin - inhibits the secretion of GH, TSH and ACTH.
HOW ? Neurohormones are released ?
from the posterior pituitary (neurohypophysis):
Vasopressin or antidiuretic hormone (ADH) or arginine- vasopressin (AVP)
Oxitocin – stimulates uterus contractions during labor.
Pituitary hormones TYPES AND CHARACTERISTICS ?
Growth hormone (GH)
The main physiologic effect is to regulate growth (overall anabolic effects).
Stimulates the hepatic production of IGF-1 (insulin-like growth factor)
ACTH- stimulates glucocorticoid and androgens secretion in the adrenal cortex
MSH - Melanocyte-stimulating hormone
Increases melanin synthesis in melanocytes.
Prolactin
The main physiologic effects of PRL are stimulation of growth and development of the mammary gland,
synthesis of milk and maintenance of milk secretion;
Thyroid- stimulating hormone (TSH)
Stimulates all the events involved in thyroid hormone synthesis and release.
In addition, it acts as a growth factor for the thyroid gland.
Gonadotropins (LH and FSH)
stimulate sex hormones synthesis,
Stimulate spermatogenesis,
Stimulate folliculogenesis and ovulation.
Thyroid hormones ? TYPES ? CHARACTERISTICS ?
T3 and T4;
under TSH regulation
Thyroid hormones play important roles in maintaining energy
homeostsis and regulating energy expenditure.
Their primary physiologic effects are to stimulate cell
metabolism and activity.
They have a vital role in the development, differentiation and
maturation of fetus during gestation.
- Calcitonin – produced by the parafollicular C-cells
Parathyroid hormone ROLE ? ACT IN RELATION WITH WHICH OTHER HORMONE ?
The main physiologic effects of PTH (parathyroid hormone) is
to regulate plasma calcium levels.
It acts in relation with other hormones:
- vitamin D
- calcitonin (produced in the parafollicular C cells of the
thyroid)
Adrenal cortex hormones NAME THE 3 DIFFERENT ZONE ? AND THEIR CHARACTERISTICS ?
The adrenal cortex contains 3 zones that vary in the steroid
hormones production :
Zona glomerulosa- mineralocorticoids
Zona fasciculata- glucocorticoids, cortisol and corticosterone
and androgens (DHEA and DHEAS)
Zona reticularis- androgens; it also produces glucocorticoids
The general metabolic effects, sexual effects, cardio- vascular
effects, etc. of the steroid hormones make them absolutely
necessary for living.
Hormones of the adrenal medulla WHAT IS IT ? AND WHAT DOES IT PRODUCE ?
The medulla is the central part of the adrenal
gland.
It produces catecholamines
norepinephrine
epinephrine and,
to a lesser extent, dopamine
The response to stress consists of ?
The response to stress consists of close
interaction between the steroid hormones
and catecholamines to ensure adequate fuel
metabolism and hemodynamic control.
Gonadal hormones WHAT DOES THIS PRODUCE ?
The testes produce:
Testosterone,
androstendione and
small amounts of estradiol
The ovaries produce
progesteron,
estrogen and
small amounts of testosterone
WHAT IS THE HORMONAL TRANSPORT ?
Secreted hormones move through the
bloodstream to endocrine target organs,
which are often distant from the initial site of
hormone release.
This represents the most important way of
hormone transport.
Hormone transport in the circulation
There are two distinct transport ways WHAT IS IT ?
The general bloodstream
The circulation at the
hypothalmo-hypophyseal portal system (both
ways).
HORMONE RECEPTORS TYPES ? BINDING TO WHAT ?
Hormones produce their biologic effects by binding
to specific hormone receptors in target cells
Membrane receptors that bind catecholamins,
peptides, proteic hormones and eicosanoids
Intracellular (nuclear) receptors that bind steroid
hormones, thyroid hormones and vitamin D.
Hormone transport 2 TYPES ?
Lipophilic hormones (steroid, thyroid
hormones)
bound to specific proteins
Unbound (free)
Hydrophilic hormones (peptidic hormones
and catecholamines) are transported
unbound, excepting for CRH and GH,
partialy bound.
WHAT IS THE Physiologic functions and the role of hormones ?
Regulation of sodium and water balance and control of blood
volume and presure
Regulation of calcium and phosphate balance to preserve
extracellular fluid concentrations required for cell membrane
integrity and intracellular signaling
Regulation of energy balance and control of fuel metabolism,
Coordination of the hemodynamic and metabolic responses to
stress
Regulation of reproduction, development, growth and senescence.
TYPE OF Disorders of the endocrine system ?
Functional disorders:
Decreased hormonal production
Increased hormonal production
Abnormal hormonal production, with abnormal effects
Receptor resistance to hormonal action
Defects in transportation or metabolisation
Complex disorders (association of hypo/ hyperfunction on
different hormonal lines).
Morphologic disorders:
with or without functional endocrine consequences,
associated disorders (neurological, ophtalmologic, respiratory).
