Transcript Endocrinology notes

Assigned readings:Chapters 1-3 in
Griffin & Ojeda; Chapter 1 in
Bentley
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Lecture: Tuesdays 6-8:45 PM
Professor: Dr. Frank V. Paladino
Office: SB G-56
Phone: 481-6304 or 6305
• Lecture 2
Thus there are 2 general patterns of hormone effects on cells
1. Protein – amine effect on membrane receptors:
Second messenger cAMP causes responses in cytoplasm
Specific Example Antidiuretic (argenine vasopressin or ADH) hormone a nonapeptide (9
aa): regulates water levels in body by action on nephron distal tubule: very close
relationship of the nonapetides secreted from the Posterior Pituitary or neurohypophysis.
2.
Steroid hormones act directly on nuclear DNA, chromosomes puff shows areas
of DNA where steroid hormone has induced new mRNA production
Cholesterol is a 17 ketosteroid and an important precursor for
all steroid hormones.
Ca also an important cell regulator and Ca – Calmodulin
system for cellular control:
• Hormone control: Usually done by
feedback loops but other general patterns;
• Pattern 1 – On/off --- For this pattern
hormone secretion is initiated by some
factor (may be neural)
For this case the hormone us usually not
found in the general circulation – some
factor turns on the secretion i.e.
Ext stim>neural signalGland> hormone
secreted>H in blood>Target organ>
response> Stimulus removed>
• Example: Food bolus in duodenum> neural
receptors Intestinal plexus> Endocrine cells
in intestinal mucosa >Secretin Hormone
dumped into blood> Receptors in pancreas>
secretin cause release of digestive enzymes
from pancreas> Food digested and
absorbed> bolus gone> Stimulus gone>
Neural signal off> secretin gone from blood
• This is an example of On/off
• Persistent secretion pattern: There is
always a certain level of the hormone in the
blood and feedback control regulates the
amount and level. Usually there are
hormone pairs that work in concert to
maintain a constant level (homeostasis) of
some chemical in system.
• SIMPLE feedback control: steady state
hormone levels control some variable
• Specific example: Regulation of blood Ca
levels
Parathormone (PTH) produced by Parathyroid glands
regulates blood Ca levels in concert with
Thyrocalcitonin (TCT) secreted from the thyroid
Levels of Ca are relatively constant in blood. PTH cells
monitor [Ca] > when [Ca]^ PTH secretion is reduced
and blood [Ca]v
PTH causes Bone cells to
reabsorb Ca from bone
matrix and deposit free
Ca in Blood , Stimulates
gut to absorb Ca and
reduces Ca secretion
in Kidney tubules
A. Thyrocalcitonin (TCT) produced by cells in thyroid nodules has
an opposite effect and opposes the action of PTH
As [Ca]^ > TCT cells in thyroid [TCT]^
TCT causes bone cells to deposit Ca in bone matrix, Kidney
tubules secrete Ca, and gut cells reduce absorption of Ca from
food.
Thus these 2 hormones are persistently secreted at low levels in
the blood and regulate very closely the levels of free Ca in the
blood. They are known as a simple negative feedback
hormone pair Feedback loop is negative because the
hormone removes the stimulus [Ca] change and thus the
system comes into steady state or homeostasis
3. Multistep feedback loops: more complex and now have feedback at more than 1 level
a. It was thought that the Pituitary gland located at the base of the brain was the “Master
Gland”
b. Embryologically derived from neural tissue and a pouch from the oral tube (Rathke’s
pouch)
Special circulation between Pituitary and Hypothalamus called Hypothalmohypophoseal portal system. Capillary’s in hypothalamus go to adenohypophysis
Tropic hormones from the Anterior Pituitary (Adenohypophysis)
and Regulating Factors (RF’s) from the Hypothalamus put
multiple levels of control and feedback in the feedback loops
1. Study and know all the Pituitary hormones and actions
2. Know the hypothalmus nuclei and regulating factors
3. Know the unique anatomy of these 2 structures
4. Understand now the multiple levels of control and
feedback
i.e. control of gonad function –
Hypothalamus produces GnRF (gonadotropin reg Factor –
goes via special circulation to Ant. Pit. Effects release of
Gonadotropin (like FTH foliculotropin AKA FSH) FSH
effects ovary – ovary produces estrogen (Female sex
hormone) estrogen effects uterus, breasts etc… and can
now feed back to hypothalamus as well as Pituitary, and
the ovary at multiple levels
Hypersecretion of thyroid
causes enlarged goiter
Exopthalmus (Bug eyes) and
Graves Disease
Hyposecretion as a child can
cause cretin as an adult
Myxedema