OPTA 222 (endocrine system)
Participates in
- regulation of digestion
- usage and storage of nutrients
- growth and development
- electrolyte and water metabolism
- reproductive functions
Involved in
- growth
- sex differentiation
- metabolism
- adaptation to a changing environment
Hormones
- Chemical messengers that are transported in body fluids
- Very specialized
- Exert action on specific target cells
-Most hormones are present in body fluids at all times but their amounts fluctuate depending on the needs of the body
- Some hormones are able to act on multiple different tissues
- Some tissues can be acted on by multiple different hormones to produce similar results
- Some hormones act locally and never travel through the blood stream
- When they act locally, it is termed a paracrine function
- When they act on the same cells from which they were produced, they’re termed autocrine
-some travel freely and others bind to a carrier molecule for transport
Stucture of Hormones
- amino acids
- protiens
- peptides
- steroids
Hormone sythesis
Some are synthesized and stored in vesicles, awaiting release
Others are released as they are synthesized
metabolism and elimination
- Hormones must be inactivated, otherwise they will accumulate
- Can be degraded by enzymes in the blood or by enzymes in the cell they are received
Receptors
- Function to recognize a specific hormone and translate the hormonal signal into a cellular response
- Response can vary based on the number of targeted receptors and also the affinity of the receptors
- Approximately 2000 to 100,000 hormone receptor molecules per cell
- Receptors can be upregulated or downregulated: Decreased hormone levels can prudence an increase in receptor numbers, Sustained levels of excess hormone often result in downregulation
Control of hormone levels
Hormone secretion varies over a 24 hour period.
- Some hormones correspond with the sleep/wake cycle
- Others are regulated by feedback mechanisms which respond to glucose etc.
Hypothalamic-Pituitary Regulation
- Hypothalamus and pituitary gland (split into anterior and posterior) form a unit and control many hormonal functions
- The synthesis and release of anterior pituitary hormones are often regulated by hormones secreted by the hypothalamus (coordination centre of the brain for endocrine function)
Feedback regulation
Most hormones are regulated by negative feedback mechanisms
- When the sensors detect a change in hormone the body adjusts secretion so that body levels are maintained in an appropriate range.: Similar to a thermostat
- Exogenous hormones can influence feedback mechanisms
- Some hormones are on a positive feedback loop, however, these usually have some type of mechanism to “shut off” hormone production
overview
Hypofunction
- Congenital defect in development of a gland or in an enzyme required for hormone synthesis
- Gland could be destroyed by infection, inflammation, autoimmune responses, neoplastic growth
- Decline in function with aging can occur
Hyperfunction
excessive stimulation and hyperplasia of endocrine gland or from a hormone producing tumor of the gland
primary
Originates in the target gland that produces the hormone
Ex. thyroidectomy
secondary
Target gland is normal but function is altered by defective levels of stimulating hormones or releasing factors from the pituitary system
tertiary
both pituitary and secreting organ are targeted
Pituitary tumors
Can be functional (produce hormone) and non functional (non hormone producing)
Range in size
Can be invasive
Small, non functioning tumors are present in up to 20% of the adult population
Growth and growth hormone disorders
Different types of hormones can be responsible for growth
Growth hormone, insulin, thyroid hormone
Growth hormone deficiency and excess in children
Deficiency in children:
Child not tracking on growth charts
With early diagnosis and treatment growth hormone replacement therapy can allow children to reach normal stature
Excess in children:
Defined as above 97th percentile
Can affect epiphyseal closure
Can be treated with hormone therapies
Growth hormone deficiency and excess in adults
Causes different outcomes in adults for both deficiency and excess than it does for children.
Excess in adults can cause acromegaly. (Andre the giant)
- Bone overgrowth leads to arthritis, kyphosis
- Enlargement of the heart and increased atherosclerosis can lead to an early death
Hypothyroidism
Congenital:
- if not detected can cause cognitive delay
Acquired:
Causes general slowing down of of metabolic processes and myxedema, accumulation of a certain type of edema throughout all body tissues
Can progress to life threatening condition
Hyperthyroidism
Tissues exposed to high levels of thyroid hormone, usually from hyperactivity of the thyroid gland. Can also be caused by:
- Adenoma of the thyroid
- Thyroiditis
Signs and symptoms:
cushings Epi
is rare
40 to 70 out of a million
Cushings Patho
Cushing’s syndrome is a disorder that occurs when your body makes too much of the hormone cortisol over a long period of time. Cortisol is sometimes called the “stress hormone” because it helps your body respond to stress.
Cushing Signs and Symtoms
- weight gain
- thin arms and legs
- a round face
- increased fat around the base of the neck
- a fatty hump between the shoulders
- easy bruising
-wide purple stretch marks, mainly on the abdomen, breasts, hips, and under the arms
- weak muscles
Cushings Treatments
Treatment depends on the cause and may include surgery, radiation, chemotherapy, or cortisol-reducing medicines. If the cause is long-term use of glucocorticoids to treat another disorder, your doctor will gradually reduce your dosage to the lowest dose that will control that disorder. Sometimes disorders that doctors treat with glucocorticoids can be treated with a non-glucocorticoid medicine instead.
Addison's Epi
is rare
100 to 140 in every 1 mill people
Addison's Patho
Addison’s disease occurs when the adrenal glands are damaged and can’t make enough of the hormone cortisol and sometimes the hormone aldosterone.
addisons signs and symptoms
- chronic, or long-lasting, fatigue
- muscle weakness
- loss of appetite
- weight loss
- abdominal pain
- nausea
- vomiting
-diarrhea
- low blood pressure that drops further when you stand up, causing dizziness or fainting
- irritability and depression
- joint pain
- craving salty foods
- hypoglycemia, or low blood glucose
- irregular or no menstrual periods
- loss of interest in sex
Addison's Treatment
- hormone replacement
- diet and nutrition
Grave's Epi
1/100
common in women
vitiligo
diabetes
rheumatoid arthritis
Grave's patho
Graves’ disease is an autoimmune disorder that can cause hyperthyroidism, or overactive thyroid. your immune system attacks your thyroid gland, causing it to make more thyroid hormones than your body needs.
Graves' Signs and symptoms
- weight loss, despite an increased appetite
- rapid or irregular heartbeat
- nervousness, irritability, trouble sleeping, fatigue
- shaky hands, muscle weakness
- sweating or trouble tolerating heat
- frequent bowel movements
- an enlarged thyroid gland, called a goiter
- eye problems
- skin problems
Graves' Treatments
medicines, radioiodine therapy, or thyroid surgery