introduction to endocrinology

Question 1

what is the definition of The Endocrine System ?

Answer 1

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.

Question 2

what is an Hormone ?

Answer 2

Chemical substance produced and secreted by one cell that travels through the blood to act on another cell.

Question 3

what contains a Target organ ?

Answer 3

contains cells that express
specific receptors and show a biologic
response after hormone binding.

Question 4

what is The components of the endocrine system ?

Answer 4

Endocrine glands

Hormones

Hormone transport pathways

Hormone receptors

Question 5

how works Endocrine glands ?

Answer 5

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.

Question 6

Answer 6

Question 7

Answer 7

Question 8

where is located the Hypothalamus ?

Answer 8

Location: Diencephalon,
integrated part of the
nervous system

Question 9

what is the role of hypothalamus ?

Answer 9

Releasing and inhibiting
hormones;

ADH, oxytocin.

Question 10

WHAT ARE THE TWO PARTS OF The Pituitary Gland (Hypophysis) ?

Answer 10

Two parts:
Anterior pituitary gland
(adenohypophysis)
Posterior pituitary gland
(neurohypophysis)

Question 11

Thyroid gland localisation ? WEIGHT ? CONSIST OF WHAT ? WHAT MAY BE PRESENT ?

Answer 11

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

Question 12

Parathyroid glands CHARACTERISTICS ?

Answer 12

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

Question 13

The Adrenal Glands CHARACTERISTICS ?

Answer 13

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.

Question 14

The Gonads THE TYPES ? AND CHARACTERISTICS ?

Answer 14

Ovaries
oval-shaped glands located asides of the uterus.
Secrete both estrogen and progesterone;
Release ovules

Testes / testicles:
produce spermatozoa
Secrete testosterone

Question 15

Classification of hormones

According to their chemical structure ?

Answer 15

Protein or peptide hormones
Steroid hormones
Amino acid- derived hormones
Eicosanoids (derived from polyunsaturated
fatty acids)

Question 16

Classification of hormones

According to their properties ?

Answer 16

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.

Question 17

Hypothalamic hormones

Hypophysiotropic neurohormones TYPES ? CHARACTERISTICS ?

Answer 17

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.

Question 18

HOW ? Neurohormones are released ?

Answer 18

from the posterior pituitary (neurohypophysis):
Vasopressin or antidiuretic hormone (ADH) or arginine- vasopressin (AVP)
Oxitocin – stimulates uterus contractions during labor.

Question 19

Pituitary hormones TYPES AND CHARACTERISTICS ?

Answer 19

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.

Question 20

Thyroid hormones ? TYPES ? CHARACTERISTICS ?

Answer 20

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.

2. Calcitonin – produced by the parafollicular C-cells

Question 21

Parathyroid hormone ROLE ? ACT IN RELATION WITH WHICH OTHER HORMONE ?

Answer 21

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)

Question 22

Adrenal cortex hormones NAME THE 3 DIFFERENT ZONE ? AND THEIR CHARACTERISTICS ?

Answer 22

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.

Question 23

Hormones of the adrenal medulla WHAT IS IT ? AND WHAT DOES IT PRODUCE ?

Answer 23

The medulla is the central part of the adrenal
gland.

It produces catecholamines
norepinephrine
epinephrine and,
to a lesser extent, dopamine

Question 24

The response to stress consists of ?

Answer 24

The response to stress consists of close
interaction between the steroid hormones
and catecholamines to ensure adequate fuel
metabolism and hemodynamic control.

Question 25

Gonadal hormones WHAT DOES THIS PRODUCE ?

Answer 25

The testes produce:
Testosterone,
androstendione and
small amounts of estradiol

The ovaries produce
progesteron,
estrogen and
small amounts of testosterone

Question 26

WHAT IS THE HORMONAL TRANSPORT ?

Answer 26

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.

Question 27

Hormone transport in the circulation

There are two distinct transport ways WHAT IS IT ?

Answer 27

The general bloodstream

The circulation at the
hypothalmo-hypophyseal portal system (both
ways).

Question 28

HORMONE RECEPTORS TYPES ? BINDING TO WHAT ?

Answer 28

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.

Question 29

Hormone transport 2 TYPES ?

Answer 29

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.

Question 30

WHAT IS THE Physiologic functions and the role of hormones ?

Answer 30

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.

Question 31

TYPE OF Disorders of the endocrine system ?

Answer 31

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).