Adrenal Gland and Hormones Flashcards
Describe the anatomy of the adrenal gland
The adrenal gland can be divided into the cortex and medulla. The cortex is on the outside, while the medulla is located deeper within the gland.
The cortex is further divided into three zonas (zona glomerulosa, zona fasiculata, and zona reticularis)
What hormones does the adrenal cortex produce?
Zona glomerulosa: secretes mineralocorticoids (aldosterone)
Zona fasiculata: secretes glucocorticoids (cortisol)
Zona reticularis: secretes sex hormones (weak androgens like DHEA and DHEA-S)
What hormones are secreted by the adrenal medulla?
The medulla secretes epinephrine and norepinephrine (induce SNS-like effects)
Epinephrine (increases blood flow to brain and muscle (HR and CO control), stimulates metabolic rate)
Norepinephrine (similar action and epinephrine, but less potent)
What are the effects of cortisol on the body?
Cortisol has widespread effects on the body:
Regulates the inflammatory response and immune system
Regulates the body’s response to stress
Regulates fat, protein, and carbohydrate metabolism
How are hormones released by the adrenal cortex regulated by the body?
The HPA axis regulates all hormones released by the adrenal cortex. The hypothalamic-pituitary-adrenal (HPA) axis is the feedback interaction of the hypothalamus, pituitary, and adrenal glands.
The hypothalamus is activated by stress, hypoglycemia, hypotension, and injury. Once activated, the hypothalamus releases corticotropin-releasing hormone (CRH). This hormone stimulates the release of hormones from the pituitary gland. The pituitary gland releases Adrenocorticotropic hormone (ACTH), this hormone stimulates the adrenal cortex to release its own hormones.
All secreted hormones from the adrenal cortex exhibit negative feedback to the hypothalamus and pituitary gland
How are hormones released by the adrenal medulla (epinephrine and norepinephrine) regulated in the body?
Release of these hormones is stimulated by fight or flight response of SNS
What is the function of hormones regulated by the HPA Axis?
The HPA axis regulates the following body processes:
Stress response
Digestion
Immune system
Mood and emotions
Energy storage and expenditure
Describe some details about cortisol secretion
10-20mg/day is released by the zona fasiculata in the adrenal cortex
Cortisol secretion is highest in the morning and declines throughout the day (lowest at midnight)
Cortisol secretion increases in response to stress
What happens to the hypothalamus and pituitary gland when cortisol levels are elevated?
Due to the HPA axis, when cortisol or other corticosteroid levels are increased (either endogenously or exogenously), secretion of CRH and ACTH by the hypothalamus and pituitary glands is inhibited. This inhibition further inhibits activation of the adrenal cortex and subsequent secretion of cortisol
Increased levels of cortisol or other corticosteroids effectively suppress the HPA axis
What is the consequence of a suppressed HPA axis?
If a patient is on corticosteroids long-term and stop taking their steroid cold turkey, the suppression of the HPA axis by the drug will severely limit the body’s natural ability to produce natural cortisol
Rank corticosteroids by potency from lowest to highest?
Short Acting/Low Potency:
Hydrocortisone
Prednisone
Prednisolone
Mrthyprednisolone
Triamcinolone
Long Acting/High Potency:
Dexamethasone
Betamethasone
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What effects the likelihood of the development of HPA axis suppression?
It largely depends on the dose, duration, and timing of steroid use.
HPA axis suppression will likely develop if it is used long-term (more than two weeks) and in large amounts (more than 15mg of prednisone equivalent per day)
It could take weeks to 1 year to recover from steroid induced HPA axis suppression
What is the best way to stop long-term use of steroids?
The doses are usually tapered off over a course of days or weeks
What is Cushing’s syndrome?
It is a condition characterized by hypercortisolemia and is usually due to:
ACTH-producing tumour (pituitary and non-pituitary)
Adrenal adenoma or carcinoma
Excess glucocorticoid use
Clinical presentation:
“Moon face”
Centripetal obesity
“Buffalo hump” fat distribution in shoulders
Personality changes
How is Cushing’s Disease treated?
Surgery on the pituitary gland is the treatment if choice (might have to put patient on corticosteroids long-term to prevent hypocortisolism)
Pharmacologic therapy is less effective
What is Addison’s Disease?
Primary adrenal insufficiency caused by destruction of up to 90% of the adrenal glands (it affects all 3 zones of the cortex)
Addison’s Disease has vague symptoms, so it can be hard to diagnose.
Common symptoms:
Fatigue
Skin hyperpigmentation
Weight loss
Salt craving
Loss of appetite
How is Addison’s disease and other types of adrenal insufficiency treated?
Chronic insufficiency (Daily glucocorticoid and mineralocorticoid replacement):
May require extra doses during stress
ex. Hydrocortisone 15-30mg/day and fludrocortisone 0.1 daily
Acute adrenal crisis (emergency situation):
IV corticosteroids and IV fluids
Describe the anatomy of the pancreas concerning the hormones it secretes
The pancreas is composed of acini and the islets of Langerhans. Within the islets of Langerhans are three cell types that produce hormones. Alpha cells produce glucagon, beta cells produce insulin, and delta cells produce somatostatin
What factors regulate insulin release?
Release stimulates by:
Glucose
Fatty acids
Amino acids
Glucagon
Ketone bodies
GLP-1
Release inhibited by:
Somatostatin
Stimulation of a2 adrenergic receptors
What factors regulate glucagon release?
Release stimulates by:
Cortisol
Exercise
Infections
Stressors
Gastrin
Insulin
Release inhibited by:
Glucose
Somatostatin
Describe the hormones involved in ovaries
The ovaries produce and secrete estrogen, testosterone, and progesterone. The release of the hormones mentioned above is stimulated by LH and FSH from the pituitary gland and inhibited by estrogen (follicular and luteal phase) and progesterone (luteal phase only)
The hormones secreted by the ovaries are responsible for sexual development and reproductive characteristics.
Describe the hormones involved in the testes
The testes produce and secrete androgens (primarily testosterone). The release of the aforementioned hormones is stimuklate
Describe the hormones involved in the testes
The testes produce and secrete androgens (primarily testosterone). The release of the hormones above is stimulated by LH and FSH from the pituitary gland and inhibited by testosterone and inhibin.
The hormones secreted by the testes are responsible for sexual development and reproductive characteristics.
