Terms in this set (90)
What is the overall goal of the endocrine system:
- Control center of the body. Ramp it up. Decrease it. Do this by using hormones
Function of the Endocrine System:
- Coordination of the Reproductive systems for Males and Females
- Stimulate growth and development
- Regulate responses to changes in metabolic needs (pregnancy, stress, trauma, infection, etc)
- Maintain Homeostasis for various chemicals and elements
_____ are the signaling molecules that transport information from one cell to another by binding to receptors
Do hormones have to work at a specific region of excretion?
Yes, but Can modify activity in a target tissue that is at some distance from the point of secretion
Are hormones long lasting?
Long-lasting biological effects due to high affinity receptor binding
What are some things that hormones and the endocrine system can do?
- Maintenance of the environment (i.e. electrolyte homeostasis)
- Coordinate/Control reproduction/sexual development
- Growth and development
- Control response to changes in energy demand (i.e flight or fight, exercise, eating)
Endocrine feedback loop:
Hormones that are produced can feedback and cut off or cut on more hormone from being released
the "control center" which regulates the function of several of the endocrine glands.
The HPA (Hypothalamic-Pituitary Axis)
The hypothalamus releases hormones into the portal blood vessels which then regulate the secretion of the
Anterior pituitary hormones
These hypothalamic hormones are:
GHRH, somatostatin, dopamine, TRH, CRH, and GnRH
These hormones then activate the hormones of the:
anterior pituitary which are listed on the slide
AdH and oxytocin are made directly in the _____ then released into ____:
supraoptic nucleus of the hypothalamus and then directly released into circulation through the posterior pituitary.
Putting it all together:
The HPA (Hypothalamic-Pituitary Axis) is the "control center" which regulates the function of several of the endocrine glands. The hypothalamus releases hormones into the portal blood vessels which then regulate the secretion of the anterior pituitary hormones. These hypothalamic hormones are GHRH, somatostatin, dopamine, TRH, CRH, and GnRH. These hormones then activate the hormones of the anterior pituitary which are listed on the slide. AdH and oxytocin are made directly in the supraoptic nucleus of the hypothalamus and then directly released into circulation through the posterior pituitary.
The important principle here is to realize that hormones signal change by BOTH:
stopping and starting the release of downstream hormones
Example of GHRH:
GHRH stimulates the release of GH from the pituitary downstream while somatostatin inhibits the release of GH.
Explanation of the feedback loop:
The principle of the feedback loop is that the downstream hormones also have receptors on the "control center" so that it can activate or suppress as needed. For instance, during a menstrual cycle, when the estrogen levels go up, they actually bind to the HPA axis and inhibit further secretion of FSH. When this feedback inhibition is lost and hormones are either allowed unrestricted release or there is a deficiency in release, it causes SEVERAL functional issues.
Symptoms you can see when a hormone is off:
The most common feedback loop with hormones is the:
Negative feedback loop, meaning what is created goes back and cuts off the system
negative feedback loop
This is where the target organ releases a hormone which binds to "control center" to cause an decrease in the stimulating hormone when the levels are in the right range.
Example of negative feedback loop:
in the picture shown, the pituitary releases Thyroid Stimulating hormone (TSH) which binds to the thyroid and causes the thyroid hormone (T3 and T4) to be released. When there is enough of both of these, they bind BACK to the pituitary and cause the TSH to shut off so that we don't get an excessive amount of hormone.
How to measure hormone values for Interpreting Diagnostic Studies for Endocrine Diseases:
- Lab Values
- Urine: 24 hour urine collection
- Genetic Testing: Long term and screening implications
The most common way that we diagnose hormone dysfunction AND the source is by measuring the hormone through a:
blood test or by a 24 hour urine collection
A 50yoF presents with c/o anxiety, sweating profusely and losing weight for no reason. She has the appearance shown in the pic:
To diagnose this clinical disease, we can order lab work. We get a TSH, ft4, ft3.
Free t4 was 4.1ng/dL (0.8-2.7ng/dL)
So if we understand the feedback loop, and the thyroid hormone is high, what can we expect the TSH to be?
- Should be non exsistant because it is cutting off in the brain or hypothalamus.
- Because the TSH is non exsistant, it means the negative feedback loop is fine, the brain is fine, but the thyroid gland is just spitting out too much hormone.
- This would be a hyperthyroidism in the gland
A 24yoM presents with increasing weight gain, weakness in his proximal muscles, and the skin findings shown...
In this case, we can order a 24 hour urine cortisol to diagnose the clinical condition
Cortisol 215mcg/24 hour (10-100mcg/24 hour)
So, knowing the hormone that controls the release of cortisol, what test can order to see where the source of excess hormone is?
ACTH is controlling the release, so we expect this to be zero
ACTH was normal, ordered scan of pituitary because the negative feedback system wasn't working. Telling you it was in the brain. Knew this because ACTH was normal
Imaging Studies for the Endocrine System:
- Nuclear Imaging Studies using specific radioactive substances
- MRI with and without contrast (pituitary)
Picture of hyperthyroid patient:
Picture of cushings patient:
Diagnosis starts by looking at the:
Endocrine Dysfunction symptoms:
Deficiency of 1+ of the pituitary hormones
Etiology: Tumor, brain surgery, radiation, stroke, TBIs, Infiltrative disease
Symptoms of Hypopituitarism
based on the hormones that are affected. I.e amenorrhea or infertility if GnRH were effected
Signs of Hypopituitary:
atrophy of genitalia, decrease in muscle tone, increase fat deposition, absent hair
How to diagnose hypopituitary:
assessment of pituitary hormone levels
Exogenous replacement of deficient hormones
Examples of Exogenous replacement of deficient hormones:
- Growth hormone, e.g. Recombinant human growth hormone
- Cortisol, e.g. hydrocortisone
- T4 deficiency, e.g. Levothyroxine
- Replacement of sex steroids
-Transdermal estrogen patch or oral replacement
- Testosterone: IM or transdermal patch or gel
Hypopituitarism PT Implications
Increase in Osteoarthritis
Decrease in muscle tone and strength (increase in fall risk)
Increase in immobility (fractures, deformities, etc)
- Acromegaly (adults after the epiphysial closure) more in skull and mandible, not in long bone bc there is no growth plate
- Gigantism (children delayed epiphysial closure) can happen in ong bones bc there is a plate
In Gigantism, there is a
delayed closure of the epiphyseal plates due to the associated hypogonadism. Thus, there is a marked acceleration of linear growth.
In comparison, acromegaly occurs in
adulthood after the epiphyseal closure in the long bones and so there is an increase is a LOCAL overgrowth of bone, especially of the skull. The clinical manifestations are a brow prominence, mandible lengthening, and soft tissue enlargement such as in the nose seen here.
Virtually all cases are due to a pituitary tumor although ectopic GH/GHRH tumors identified.
early: heat intolerance, sweating, weight gain, oiliness of the skin
: enlarging of hands/feet (ring/shoe size suddenly change), wide spaced bottom teeth, skin tags
: elevated IGF1, glucose suppression test
standard of care:
Inhibit GH secretion, GH receptor antagonist)
Gamma knife radiation
Physical Therapy Implications:
- Arthritis of hands
-Irreversible even with therapy
- Osteoarthritis of spine
- Carpal Tunnel Syndrome
-Enlargement of soft tissue cause median nerve compression
Normally, ADH helps
regulate the water balance in the body
Excess Syndrome (SIADH):
Increase the absorption of free water in response to changes in blood volume and blood pressure
malignancy, infections, medications (SSRIs, opioids)
AMS (irritability, confusion, sluggishness), weakness, muscle cramps
nausea, malaise, HA, and obtundation
Hyponatremia with Na <125mEq/L, Uosm >100
- Correction of Sodium Imbalance
-Water restriction, hypertonic saline
- Treat Underlying Cause
- Tumor resection, radiation, discontinue offending medication
Lithium and demeclocycline (cause nephrogenic block of ADH)
Vaptans: ADH antagonists
Changes in urination and fluid intake
Assessments for safety at home with falls, confusion (elderly)
Decrease in mobility due to increase in edema
Avoid use of ASA or NSAIDs
Deficiency Syndrome (Diabetes Insipidus)
Kidney Tubules fail to reuptake the water
With diabetes insipidus you will urinate:
VERY dilute urine.
destructive pituitary neoplasm (or mets from breast/lung), head trauma, radiation, medications (chemotherapy
Polyuria (atleast 2.5L/day but can get upto 10L per day!), polydipsia, dehydration, nocturia
AMS, dehydration, orthostatic hypotension
Serum Osm >295-300, Urine Osm <100, ADH
Central: dDAVP (ADH analogue)
Nephrogenic: thiazide diuretics
Restore free water deficit
Frequent nighttime urination with fall risk
Thyroid Excess Syndrome
Secondary or Primary
If due to pituitary what will the labs be? If because of the thyroid?
If due to pituitary what will the labs be? If because of the thyroid?
What does thyroid do?
Normal growth and development, regulate metabolism for energy, thermogenesis, bone and skin growth/regeneration
"Hot nodule", autoimmune, iodine excess (contrast), exogenous abuse
weight loss, heat intolerance, sweating, palpitations, hypercoagulable
tachycardia, flushing, proptosis, lid lag, tremor
TSH and free t4 levels, I-123 nuclear scan
Hyperthyroidism: PT Implications
- Muscle atrophy and proximal muscle "myopathy"
- Vital Signs: risk of CHF and afib with excess exercise
- Weakness of respiratory muscles
Autoimmune, iodine deficiency, nuclear radiation (Chernobyl or Japan)
cold/dry skin, sluggish, irregular menses, abnormal weight gain, delayed speech
delayed reflexes, muscle cramps, constipation
TSH and free t4 levels
Hypothyroidism PT Implications
Myalgias and arthralgias
Link between hypothyroidism and fibromyalgia
If due to pituitary what will the labs be? If because of the adrenal glands
If due to pituitary what will the labs be? If because of the adrenal?
Responsible for homeostasis during physical stress. "Fight or flight".
Outer layer of adrenal:
Cortex releases what?
releases glucocorticoids (cortisol), mineralocorticoids (aldosterone) and precursors to DHEA
Inner layer of the adrenal:
catecholamines (epinephrine and norepinepherine.)
enlarged, going back to thyroid
What does cortisol do?
- Life-sustaining hormone
- Increases gluconeogenesis
- Decreases calcium reabsorption in the kidney
- Inhibits GH secretion
- Cause muscle fiber lysis