Download Endocrine_Lecture

This material IS testable. I would expect Multiple Choice questions, true false questions and a matching section
based upon this summary.
(1) Hormones are chemical signals synthesized and released by SOURCE cells/glands into the bloodstream so that
they can be carried to the TARGET cells. To be a target cell, there USUALLY must be a specific receptor for that
hormone. HOWEVER, there are cases of non-specific actions of some hormones that occur in the absence of any
receptors systems.
(2) Hormones which bind to cell-surface receptors do so because these hormones have some feature(s) which
prevent them from crossing the membrane. (Usually this is because these hormones are protein). In the event that
hormones can not cross the membrane, they bind to a surface receptor which activates a SECOND MESSENGER
SYSTEM. These 2nd messenger systems were discussed previously. IE. cAMP, IP3/DG, Ca++
(3) The PRIMARY Endocrine organs include:
-Pineal Gland
-Hypothalamus
-Pituitary Gland .. also called the hypophysis
-Thyroid Gland
-Parathyroid Glands
-Thymus
-Adrenal Glands
-Pancreas (some regions of this organ are also exocrine)
-Testes/Ovaries (some regions of these organs have exocrine function)
-Placenta
-Corpus Luteum ... The Placenta and CL are considered Transient Endocrine Glands.
(4) The SECONDARY Endocrine organs include:
-Skin
-Heart
-Stomach
-Liver
-Small Intestines
There is a special relationship between the Hypothalamus and the Pituitary Gland. This was describe extensively
by anatomists and physiologist of the early to mid 1900's. Work on the endocrine relationship was accelerated
until the 1970-80's. Wisloki and King, Harris et al, Schally et al. .. even Dr. Mallory did some important work on
the control of the hypothalamic/pituitary axis in the 1980's..
The Hypothalamo-hypophyseal portal blood system:
The Primary Portal Plexus (capillary bed) resides in the hypothalamus and is impinged upon by hypothalamic
neurons. These neurons release neurohormones into the bloodstream within the capillaries. The portal vasculature
carries the neurohormones to the Anterior lobe (pars distalis) of the pituitary gland where they interact with target
cells. The image above depicts that relationship for Growth Hormone Releasing Hormone (GHRH) an
hypothalamic neurohormone, and the cells (Somatotropes) of the pars distalis that synthesize/release Growth
Hormone (GH). A list of other hormones will be provided below.
In addition to the Hypothalamo-hypophyseal portal system, the hypothalamus can interact directly with the
posterior lobe of the pituitary (pars nervosa) by long axons extending from cell bodies located in the hypothalamus
through the pituitary stalk and terminating on cells of the pars
nervosa. Two neurohormones are synthesized in the hypothalamus
and secreted into the blood stream via the pars nervosa. These
hormones are Oxytocin and Vasopressin (also called Antidiuretic
hormone, ADH).
Lactotropes: Cells of the pars distalis which synthesis prolactin
Thyrotropes: Cells of the pars distalis which synthesis thyrotopin
Corticotropes: Cells of the pars distalis which synthesis ACTH
Somatotropes: Cells of the pars distalis which synthesis GH
Gonadotropes: Cells of the pars distalis which synthesis LH/FSH
SOURCE
HORMONE
TARGET
ACTION
Hypothalamus
Prolactin Releasing Hormone
Lactotropes
Stimulate Prolactin (PRL) synthesis and
release
Dopamine
Lactotropes
Inhibit PRL synthesis and release
Thyrotropin Releasing
Hormone (TRH)
Thyrotropes
Stimulate Thyroid Stimulating Hormone
(TSH) synthesis and Release
Corticotropin Releasing
Hormone (CRH)
Corticotropes
Stimulate Adrenocorticotropic Hormone
(ACTH) synthesis and release
Growth Hormone Releasing
Hormone (GHRH)
Somatotropes
Stimulate Growth Hormone (GH)
synthesis and release (also called
Growth Hormone Inhibiting
Hormone (GHIH)
Somatotropes
Inhibit GH synthesis and release
Gonadotropin Releasing
Hormone (GnRH)
Gonadotropes
Stimulate Luteinizing Hormone (LH) and
Follicle-Stimulating Hormone synthesis
and release
Oxytocin
PARS NERVOSA
Stimulate uterine contractions, milk
ejection in Female, unkown in male
Antidiuretic Hormone (ADH)
also called Vasopressin
Distal convoluted
tubule of kidney
stimulates additional reabsorption of
water, reduces amount of urine produced.
Melatonin
many
biorhythms, sleep cycles
This may be TRH
Pineal Gland
somatotropin)
stimulate milk production, gamete
Prolactin (PRL)
breasts, gonads, etc
production etc
Thyroid stimulating hormone
(TSH) also called thyrotropin
Thyroid cells
stimulates production of triiodothyronine
(T3) and tetraiodothyronine (T4)
Adrenocortioctopin (ACTH)
Zona fasciculata
and Zona reticularis
of Adrenal Cortex
stimulates cortisol synthesis and release.
Growth Hormone (GH)
Somatic Cells &
hepatocytes (liver)
stimulates liver to secrete IGF=s and
direct action on bone and soft tissue
growth
Luteinizing Hormone (LH)
Thecal cells of
ovaries and Leydig
cells of Testes
stimulate the production of testosterone
and the mass of the gonads
Follicle-Stimulating Hormone
(FSH)
Granulosal cells of
ovaries and Sertoli
cells of testes
stimulates aromatase enzyme activation
leading to production of Estrogen by the
granulosal cells. Stimulates Sertoli cells
to nourish sperm. Stimulation of
INHIBIN by both ovaries and testes.
Thymus (not very
active in adult)
Thymosin
Immune system
T-cell function
Thyroid gland
T3 and T4
most body cells
regulates metabolic rate
Calcitonin
bone
increase calcium uptake by bone,
therefore decreasing blood calcium
Parathyroid glands
Parathyroid hormone (PTH)
bone, gut, kidney
increases blood calcium by increasing
bone to release calcium, increasing
calcium absorption across gut and at the
nephron
Adrenal Cortex
Zona glomerulosa
Aldosterone
distal tubules of
nephron
stimulates reabsorption of sodium
Adrenal Cortex
Zona fasciculata
Cortisol
many body cells
regulates bodys response to stress,
etc
Adrenal Cortex
Zona reticularis
Androgens (testosterone like
steroids)
many body cells
increase muscle mass, increase
lipolysis etc
Adrenal Medulla
Epinephrine
Pancreas:
Cells
Insulin
somatic cells and
hepatocytes
increase somatic cell uptake of
glucose, promotes protein, lipid, &
glycogen synthesis
Pancreas:
cells
Glucagon
somatic cells,
hepatocytes
decrease cell uptake of glucose,
promote glycogen breakdown into
glucose,
Pancreas:
-cells
somatostatin
several
regulate digestion, absorption of
nutrients, regulate pancreas
Pars Distalis
sympathomimetic
Testes:
Leydig cells
Testosterone
somatic cells
anabolism, regulate reproductive
functions, terminate bone growth
Testes:
Sertoli cells
Inhibin
pars distalis
decrease FSH secretion
Ovaries:
Granulosa
Estradiol
somatic cells,
feminizing hormone
Inhibin
pars distalis
decrease FSH secretion
Ovaries:
Progesterone/Estradiol
reproductive
system
promotes gestation
human chorionic gonadotropin
CL
maintains CL function
Corpus Luteum
(CL)
Placenta
See text for description of secondary organs (pages 170-171)
Images of people afflicted with various endocrine disorders:
Excess GH: Acromegaly
GH deficiency: Dwarfism
================================================================================
Adrenal hypofunction: Addisons Disease
hyperpigmentation
John F Kennedy had Addison=s disease
excess pigmentation of lips from AD
Excess Cortisol: Cushing=s Syndrome or Disease
Obesity from Cushings
Hyperthyrodism: Graves disease.
Striea from excessive stretching due to Cushings