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Module 09: General Medical Knowledge, Section 2: The Endocrine System
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
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Module 9: General Medical Knowledge
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Section 2: The Endocrine System
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Exocrine glands / endocrine glands
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The Pituitary Gland
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regulates other glands
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pituitary tumor
optic chiasm
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pituitary adenoma
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optic nerve compression
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The Thyroid Gland
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bitemporal hemianopsia
controls rate of metabolism
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hyperthyroidism (Grave's disease)
ocular effects
hypothyroidism
ocular effects
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The Parathyroid Glands
regulates blood calcium levels
The Adrenal Glands
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
regulate blood volume, heart function, and sexual characteristics
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The Pancreas
*These courses are not sponsored
secretes digestive enzymes and regulates blood glucose levels with insulin and glucagon
by JCAHPO® ; only reviewed for
compliance with JCAHPO®
Diabetes
standards and criteria and awarded
types I and II
continuing education credit
accordingly; therefore, JCAHPO®
diabetic eye diseases
cannot predict the effectiveness of
the program or assure its quality in
diabetic retinopathy
substance and presentation.
common drugs
JCAHPO® , COA ® , COT ® , and
COMT ® are registered trademarks
the Joint Commission on Allied
Health Personnel in Ophthalmology
Copyright © 1998-2012 eyetec.net The endocrine system is made up of glands that secrete hormones that
chemically regulate different bodily actions and processes. It is the job of the
endocrine system to maintain stability in response to changes in the internal and
external environment.
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There are two types of glands in the body. Exocrine glands, such as sweat
glands, excrete through ducts. Endocrine glands excrete hormones into the blood
stream. Specific tissues in the body are sensitive to and are affected by changing
concentrations of specific hormones in the blood.
reserved. No part of this site may b
reproduced, stored, or transmitted i
any form or by any means without
The Pituitary Gland
the written permission of the
publisher except for brief
quotations. The Pituitary Gland is located at the base of the brain
where it works in conjunction with the hypothalmus to
regulate many other glands in the body. It’s location
near the optic chiasm has significance in
ophthalmology because a pituitary tumor can enlarge
and put pressure on this crossing point of the optic
nerves, resulting in visual field defects.
Some of the hormones released by the pituitary gland,
and their effects, are as follows:
Antidiuretic hormone (ADH): Causes the kidneys
to stop taking water from the blood if there is little
water intake and the blood becomes too thick.
Oxytocin: Causes milk letdown from the mother’s
breast when an infant sucks on his mother’s
breast.
Growth hormone: Stimulates growth during
childhood.
Thyroid simulating hormone (TSH): Causes the
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
thyroid gland to produce thyroxine.
Adrenocorticotropic hormone (ACTH): Causes
the adrenal gland to release other hormones.
Pituitary Adenoma is a common tumor of the pituitary
gland that can change hormone production levels and
can grow into the space of the nearby optic nerves. The
ophthalmic patient may complain of visual field loss and
headaches. Optic nerve compression can result in
optic atrophy and permanent field loss (bitemporal
hemianopsia). Pituitary Adenoma can be treated with
drugs, radiation, and surgical removal.
The Thyroid Gland
The thyroid gland is located in the throat, just below the
larynx. This gland secretes thyroxine which controls the
rate of metabolism. A lack of thyroxine during infancy
can result in physical and mental impairment.
Hyperthyroidism (Grave’s disease) is caused by an
overactive thyroid gland. The increased level of
thyroxine causes increased metabolism which may result
in anxiety, abnormal heart rhythms, increased appetite,
and weight loss. It can be treated with drugs, radiation, or
surgical removal.
Ocular effects are due to inflamed and swollen
extraocular muscles which may push the eyeballs
outward (exophthalmos). This can cause exposure
keratitis secondary to lid retraction, and optic nerve
compression which can result in decreased vision.
Hypothyroidism is caused by an underactive thyroid
gland, resulting in an abnormal slowing of metabolism. Ocular effects may include conjunctival and corneal
swelling, keratoconus, cataracts and optic atrophy. It is
treated by taking the hormone orally.
The Parathyroid Glands
There are four parathyroid glands located next to the
thyroid gland. These glands secrete parathormone
(PTH) which regulates blood calcium levels by taking
calcium from bones and by limiting calcium excretion by
the kidneys. The Adrenal Glands
The adrenal glands (A) are located on top of the kidneys (K). The outer part of the glands (the cortex) secretes:
Aldosterone: Causes kidneys to retain sodium in
the blood, thus maintaining blood volume, and
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
causes kidneys to take potassium from the blood,
thus maintaining proper heart function.
Cortisol: Regulates metabolism and blood
pressure.
Androgens: Hormones that affect sexual
characteristics.
The adrenal glands also secrete epinephrine (adrenaline)
and norepinephrine which affect alertness and heart rate. The Pancreas
The pancreas (P) is located near the stomach . It
secretes digestive enzymes into the intestines and
produces insulin and glucagon. Insulin and glucagon
hormone levels in the blood cause cells to take glucose from the blood (insulin) or release glucose into the blood
(glucagon) to keep blood glucose within a normal range.
Diabetes
Diabetes mellitus results when blood sugar levels stay too
high due to an abnormal decrease in insulin production, or
when the insulin produced is ineffective.
Ten percent of diabetics are Type I (juvenile onset, insulin
dependent), which begins before age 35 and is caused by a
destruction of the beta cells that produce insulin. This can be
caused by genetic factors, viral infection of the pancreas, or an
immune system gone awry. These patients have to take
insulin.
Type II diabetes (adult onset) generally begins after age 35.
Insulin levels may be normal but the body does not use the
insulin to maintain proper blood sugar levels. The pancreas
eventually decreases insulin production, making the situation
worse. Genetics and obesity are major factors. Treatment
involves diet control, exercise, and oral medications.
Types of diabetic eye disease
Cataracts — Diabetics are twice as likely to develop
cataracts and they develop cataracts at an earlier age than
non-diabetics.
Glaucoma — Diabetics are twice as likely to develop
glaucoma as the general population.
Diabetic retinopathy — This is a disease of the retinal blood
vessels. It is thought that hyperglycemia (increased levels of
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
sugar in the blood) alters retinal blood vessel metabolism. Blood platelets become abnormally sticky and retinal blood
vessels narrow. Diabetic retinopathy is a leading cause of
blindness. According to the National Institute of Health, the U.S. has 16
million diabetics, and half of them have some stage of diabetic
retinopathy. About 8% of those with diabetic retinopathy have
retinopathy at a vision loss stage. Advanced diabetic
retinopathy is the leading cause of blindness among working
age Americans, with 25,000 patients developing blindness
each year from the disease.
There are three important risk factors for the development
of vision threatening diabetic retinopathy:
Fluorescein angiogram of
diabetic retinopathy. Click on the
image for an enlarged view. Use
Type of diabetes — Type I diabetics are more likely
to develop diabetic retinopathy than Type II diabetics.
the back button on your browser
to return.
Duration of diabetes — The longer you have
diabetes, the more likely you are to develop serious
diabetic retinopathy.
Blood sugar control — Diabetics with poor control of
their blood sugar levels are more likely to develop
significant diabetic retinopathy.
Fluorescein angiogram of
proliferative diabetic retinopathy.
Almost all Type I diabetics with diabetes for more than 15
years have diabetic retinopathy. Type II diabetics who are on
insulin and have had diabetes for more than 20 years have a
50% chance of developing proliferative diabetic retinopathy.
Once a diagnosis of diabetic retinopathy has been made, the
ophthalmologist may use the results and guidelines of various
studies to guide the treatment of the disease with laser
photocoagulation of the retina.
Fluorescein angiogram showing
laser scars in the treatment of
diabetic retinopathy.
Most patients will volunteer whether or not they are diabetic,
but some do not. Ask patients specifically if they are diabetic,
or if their doctor considers them to be a "borderline" diabetic.
The following are some common non-insulin anti-diabetic
drugs. Some patients who take some of these drugs do not
consider themselves to be diabetic. Being aware of these
drugs will tip you off to a patient with blood sugar problems if
they do not volunteer the information. Most of these are
common medications, and some are available in generic
form. Pay attention to the spelling of the generic as well as
the trade name so that you can spell the names correctly in
the chart.
Amaryl (glimepiride)
Diabeta (glyburide)
Glucophage (metformin)
Glucotrol (glipizide)
Glynase (glyburide)
Prandin (repaglinide)
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Module 09: General Medical Knowledge, Section 2: The Endocrine System
Precose (acarbose)
Rezulin (troglitazone)
The type of diabetes, the duration of the disease, and blood
sugar control are major risk factors in the development of
vision-threatening diabetic retinopathy. The ophthalmologist
will want to know the answer to the following questions:
At what age were you diagnosed with diabetes?
Do you take insulin? How long have you been on
insulin?
If the patient doesn't take insulin: What medication do
you take, or are you diet controlled?
Is your blood sugar under good control?
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