HPA axis Flashcards
Neuro Week 11
Is the Pituitary part of the brain?
No, it’s a gland attached to the hypothalamus but not technically a part of the brain= main ways brain communicates to rest of body
HPA Axis- works through hormones to communicate in bloodstream to organs
how does the pituitary gland grow from childhood to adulthood
- ingrown oral epithelium known as Rathke pouch as an extension of the developing oral cavity
- eventually cut off from origin of growth by sphenoid bone and settles in sella turcica (saddle shaped, base of brain, bone depression)
- rapid growth in childhood and adult (20s) slower growth
Anterior pituitary/adenohypophysis is responsible for nerves that release hormones or hormone release?
hormone release (adrenal gland)
posterior pituitary gland/ Neurohypophysis controls nerves or hormone release?
nerve stimulation that direct hormone release (nerves)
Which pituitary is larger?
anterior- accounts for most of glands size and weight
helps children grow, plays a role in metabolism, bone and muscle health, fat distribution in adults
controls body proportion in extremities and jaw, controls bone growth and height
Growth hormone function
stimulates breast milk production, impacts sex drive and sperm count in men
prolactin
plays a different role whether you have testes or ovaries- sex development and reproduction
In females: stimulates the ovaries to produce eggs and follicles, and helps manage the menstrual cycle.
In males: stimulates the testes to produce sperm
follicle stimulating hormone (FSH)
plays a different role whether you have testes or ovaries
In women: triggers ovulation, the release of progesterone, and the production of steroid hormones in the ovaries.
A sharp increase in levels, known as an ___ surge, occurs around the time of ovulation.
In men: causes the testes to produce testosterone and the Leydig cells to grow.
Regulation: is regulated by gonadotropin-releasing hormone (GnRH), which is produced in the hypothalamus.
luteinizing hormone (LH)
controls production of cortisol; natural steroid needed to stimulate the adrenal gland to release other hormones that regulate blood pressure, blood sugar, and metabolism
Adrenocorticotropic hormone (ACTH)
prompts the thyroid gland to produce thyroid hormones controlling functions such as metabolism, heart rate and appetite
thyroid stimulating hormone
where do most pituitary adenomas develop?
adenohypophysis/ ant pituitary- usually benign and successfully treatable
how common are pituitary tumors in primary brain tumors?
pituitary tumors account for 12-19% of primary brain tumors (3rd most common primary brain tumors in adults). Inc risk with age mostly after 30s.
They are classified by if they secrete excessive amounts of pituitary hormones or not.
It may inc hormone production from the cell it arises from or may dec production of hormones from other cells
which type of radiological workup is the best imaging technique for detecting pituitary tumors CT or MRI?
MRI - 100% sensitive and 91% specific
CT- 17-22% sensitive
This HPA ds is prevalent in older individuals but in increasing in children. It parallels to obesity incidence and is highest in Americans.
Metabolic disorder
- abdominal obesity (inc in waist circumference)
- high blood pressure
- high blood sugar - can damage blood vessels and inc risk of blood clots
- high triglycerides- inc LDL (risk of atherosclerosis)
- low HDL cholesterol- low levels of HDL (good cholesterol) - make it harder for body to remove bad cholesterol
3/5 of these would be diagnosed with what disease?
Metabolic syndrome
what ds has these symptoms:
- polyuria- inc urine
- polydipsia- excessive thirst
- polyphagia- excessive eating
(present in DM- main component)
Metabolic syndrome
Mechanism of ds: insulin resistance and adipose dysfunction, chronic inflammation
(impaired insulin secretion- impaired glucose metabolism, fat deposition, cardiotoxicity and chronic inflammation)
Metabolic disorder
acromegaly symptoms
- enlarged hands and feet
- gradually changes in face shape - protruding lower jaw and brow bones
- enlarged nose
- thickened lips
- frequent headache
- excessive perspiration
- hypertension
- sleep apnea
etc
mechanism of acromegaly
chronic exposure to excess GH from somatotroph pituitary adenoma
- excessive GH and it targets IGF-1
- typically benign
- changes occur gradually leading o delayed diagnosis
central ___________ is most common which affects secretion of ADH from the posterior pituitary
diabetes insipidus
symptoms of DI
- polyuria/ nocturia
- polydipsia- thirsty
- nausea and vomiting
- dizziness, fatigue, light headiness
- dry mouth, dry lips
common in children- vision, delayed growth, weight loss, constipation, fever and vomiting
endocrine ds affecting posterior pituitary hormone ADH/vasopressin- body cannot regulate water balance, leading to excessive thirst and excreting large amounts of diluted urine, not related to blood glucose
Diabetes insipidus
__________ __________occurs when there is either a deficiency in ADH production or an impaired response to ADH in the kidneys. This leads to a lack of water reabsorption, resulting in the production of large volumes of dilute urine and dehydration.
Diabetes insipidus
4 types of DI:
- Central DI: NO ADH
This type is due to a deficiency of ADH, often from damage to the hypothalamus or pituitary gland caused by tumors, head trauma, infection, or surgery. Without adequate ADH, the kidneys cannot retain water. - Nephrogenic DI: Kidneys do not respond to ADH
This form occurs when the kidneys do not respond to ADH, even though it is present in sufficient amounts. Causes include genetic mutations, chronic kidney disease, or drugs (e.g., lithium). - Dipsogenic DI: lots of fluid supress ADH
Caused by a malfunction in the thirst mechanism within the hypothalamus, leading to excessive fluid intake that suppresses ADH release. - Gestational DI: Placenta enzyme breaks down ADH
A rare type occurring during pregnancy when an enzyme produced by the placenta breaks down ADH, leading to its deficiency.
Clinical Manifestations of DI
The lack of ADH effect in DI leads to the production of excessive, dilute urine. The body’s response to dehydration is increased thirst, aiming to replace lost water. If fluid intake does not match urine output, dehydration, and electrolyte imbalances can occur, leading to complications like low blood pressure, confusion, and kidney dysfunction.
Addison’s ds is more common in females or males?
females
Addison’s ds
primary adrenal insufficiency- the adrenal glands produce insufficient amounts of cortisol and aldosterone= affects adrenal cortex, which produces critical hormones controlling metabolism, blood pressure regulation, and the body’s response to stress
what is the most common cause of addisons ds?
**autoimmune destruction of the adrenal cortex - accounting for 70-90% of cases
addisons ds symptoms
insidious and gradual onset of nonspecific symptoms
Initial presenting features
1. Fatigue, generalized weakness, weight loss, nausea, vomiting, abdominal pain, dizziness, tachycardia, and hypotension
2.** Hyperpigmentation of skin and mucous membranes**
Commonly diagnosed after hospitalization of acute adrenal crisis
1. Hypotension, hyponatremia, hyperkalemia, and hypoglycemia
● Hypotension (low blood pressure)
● hyponatremia (low sodium)
● hyperkalemia (too much potassium- chemical that nerve and muscle cells (including those of the heart) need to function= muscle weakness, palpitations, numbness, chest pain, nausea, vomiting, and trouble breathing)
● hypoglycemia (low blood sugar) can occur together in adrenal crisis, a severe endocrine emergency
treatment addisons ds
acute- 100 mg of hydrocortisone should be administered intravenously or intramuscularly
chronic- lifelong hormonal replacement therapy
Addison’s Disease-Mechanism of Disease
- Leads to decreased adrenocortical hormones which include cortisol, aldosterone and androgens- control metabolisms, stress response and bp (aldosterone-affects fluid balance)
- Results in increased adrenocorticotropic hormone (ACTH) and melanocyte stimulating hormone (MSH) due to the loss of negative feedback inhibition
- Insidious course of action presents with a glucocorticoid deficiency followed by mineralocorticoid deficiency
most common cause of Addison’s disease is
autoimmune adrenalitis—an immune response in which the body’s immune system mistakenly attacks the adrenal cortex, damaging the cells responsible for producing cortisol and aldosterone.
Low cortisol levels= impair body’s ability to regulate blood glucose and manage the stress response. symptoms like fatigue, muscle weakness, low blood sugar, and poor stress tolerance.
lack of aldosterone disrupts sodium and potassium balance, causing the kidneys to excrete too much sodium while retaining potassium leading to low blood pressure, dehydration, and electrolyte imbalances, which contribute to symptoms like dizziness, salt cravings, and weakness
what is cushing’s ds?
Excessive ATCH leading to hypercortisolism
too much cortisol:
- Increased blood sugar: Cortisol raises blood glucose levels by stimulating the liver to release stored sugar, potentially leading to diabetes if chronically elevated.
- Fat redistribution: Excess cortisol can lead to fat accumulation in the abdomen and upper body, creating a “buffalo hump” between the shoulders while thinning the limbs.
- Muscle breakdown: Cortisol promotes muscle protein breakdown to provide energy during stressful situations, leading to muscle weakness when levels are persistently high.
can be from pituitary adenoma (80%) leading to excessive release of ATCH from ant pituitary
Patient Population cushing’s ds
3x more common in women
average age of onset is 40 years old
Pituitary ATCH dependent cushings disease causes ____ % to ____ % of cushings ds
60-70 %
what other comorbidities is Cushing’s ds associated with?
diabetes (blood sugar/energy), hypertension (bp), clotting disorders
