Adrenal Glands form/functions Flashcards
Spring 2024
Adrenal gland
The adrenal gland is composed of two embryologically distinct tissue —the outer adrenal cortex and inner adrenal medulla.
Where are the adrenal glands located?
On each kidney
Adrenal cortex
- Functions to produce steroid hormones
- Is the outer portion
- Has 3 layers
Adrenal medulla
- Functions to produce amine hormones
- Inner portion
List the 3 adrenal cortex zones
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Zona glomerulosa
- Secretes mineralocorticoids, such as aldosterone
- Critical for salt balance, potassium excretion, acid–base homeostasis, and regulation of blood pressure
Zona fasciculata-
- Secretes glucocorticoids such as cortisol
- critical for carb metabolism and blood pressure
Zona reticularis
- Secretes sex hormones such as the androgens
- Required for sexual function and contribute less than the gonads
Aldosterone
Where is it produced?
Function?
How is it regulated?
- Produced in G-zone
- Controls amount of fluid in body (Na, Cl, and water retention, K and H excretion)
- renin-angiotensin system controls its production
How does decreased aldosterone affect Na and K excretion?
Increases Na excretion
Decreases K excretion
How does increased aldosterone affect blood pressure, blood volume, and reabsorption?
Increases salt and water reabsorption and increases blood pressure/volume (vasoconstriction)
Describe aldosterone regulation by renin
Increased BP and blood volume suppresses renin secretion, thus suppressing aldosterone synthesis
Describe primary hyperaldosteronism
It’s an adrenal disease, such as an aldosterone-secreting adrenal adenoma or carcinoma, or adrenal cortex hyperplasia
Conn syndrome
Aldosterone-secreting adenoma
Describe secondary hyperaldosteronism
Renin-angiotensin disorder where there’s excess renin synthesis due to renin-secreting renal tumor, thus causing malignant hypertension
Primary aldosteronism “Conn’s Syndrome”
- Increased sodium levels
- Symptoms: hypokalemia, mild metabolic alkalosis, increase blood volume and BP
Hypoaldosteronism
Atrophy of adrenal glands
Examples of hypoaldosteronism
- Addison’s disease: reduced aldosterone and glucorticoid production
- Congenital deficiency of 21-hydroxylase enzyme
Consequences of hypoadrenalism
- Reduced aldosterone and cortisol secretion
- Reduced blood glucose
- Reduced Na and Cl
- Increased ACTH
- Increased beta-MSH
- Increased K
- Skin pigmentation
- Muscle weakness
- Weight loss
- Decreased BP
- Nausea
- Diarrhea
Addison’s disease signs
- Bronze skin
- Changes in body hair distribution
- GI disturbances
- Weakness
- Weight loss
- Hypoglycemia
- Postural hypotension
Cortisol physiological effects
- Anti-insulin effects of carbs -> increased blood glucose
- More gluconeogenesis, lipolysis, protein catabolism
- Less protein synthesis, antibody formation, inflammatory response
Which two hormones have diurnal variation?
Cortisol and ACTH
Cortisol regulation
Positive feedback loop
Hypothalamus secretes CRH -> anterior pituitary secretes ACTH -> adrenal gland secretes cortisol, which goes back to stimulate the hypothalamus
How do cortisol levels affect ACTH release?
Low cortisol = more ACTH released
High cortisol = less ACTH released
Primary hypercorticolism
- Adrenal adenoma or carcinoma
- Cushing syndrome results from cortisol excess
Secondary hypercorticolism
- Pituitary tumor causes excess ACTH production
- Ectopic production of ACTH by nonendocrine tumor
- Cushing disease results from pituitary ACTH excess, which in turn stimulates too much cortisol
Cushing’s Syndrome symptoms
- Increased symptom cortisol
- No diurnal variation
- Hyperglycemia
- Reduced ACTH and immune response
- Belly and face weight gain (moon face)
- Buffalo hump back
- Thinning skin
- Easy bruising
- Hypertension
- Muscle wasting
Difference between Cushing’s Disease and Syndrome?
- Cushing’s Disease: this is an actual disease in which there is an adenoma on the pituitary gland causing too much ACTH made, thus too much cortisol
- Cushing’s Syndrome: This is a syndrome that has various symptoms associated with high levels of cortisol or corticosteroids in the body
ACTH levels in Cushing’s Disease and Syndrome
CD: always high
CS: not always high
Causes of ACTH-dependent Cushing’s Syndrome
- Primary ACTH pituitary disease
- Ectopic ACTH
- Ectopic CRF
Causes of ACTH-independent Cushing’s Syndrome
- Adrenal adenoma
- Adrenal carcinoma
- Nodular adrenal hyperplasia
- Exogenous glucocorticoids
Primary hypocorticolism
Atrophy of adrenal gland due to
-autoimmune disease
-tuberculosis
-prolonged high dosage cortisol therapy
Secondary hypocorticolism
Pituitary hypofunction
Criteria for primary adrenal insufficiency when cortisol is low
- None to minimal cortisol stimulation
- High ACTH
- Low aldosterone
- Hyperkalemia/hyponatremia
Criteria for secondary adrenal insufficiency when cortisol is low
- Normal cortisol stimulation
- Low ACTH
- Normal aldosterone
- Normal electrolytes
Adrenal medulla produces which catecholamines?
- Epinephrine
- Norepinephrine
- Dopamine
How are catecholamines made?
Synthesized from tyrosine by chromaffin cells of the medulla, brain, and sympathetic neurons
Epinephrine
- Converts glycogen to glucose, which allows voluntary muscles to have greater work output
- Released in response to low BP, hypoxia, cold exposure, muscle exertion, and pain
Norepinephrine
- Neurotransmitter affecting vascular smooth muscle and heart
- Released primarily by postganglionic sympathetic nerves
Dopamine
Neurotransmitter in brain affecting vascular system
Catecholamine metabolism
:)
Pheochromocytoma
- Benign tumor of adrenal medulla
- Increased epinephrine and norepinephrine
- Quantified by fluorometric, colorimetric, spectrophotometric methods
Fluorometric methods quantify…
Plasma epinephrine and norepinephrine
Colorimetric/spectrophotometric methods quantify…
VMA
Neuroblastoma
- Malignant tumor of adrenal medulla common in kids
- Makes epinephrine, norepinephrine, dopamine, and HVA
- Characterized by increase in HVA and VMA urinary excretion
- Quantified by HPLC, gas chrom, and spectrophotometry
Adrenal incidentaloma
Adrenal madd greater than 1 cm
Testes
- Part of hypothalamic-pituitary-gonadal axis
- Anterior pituitary secretes LH and FSH
LH
Stimulates production of testosterone
FSH
Stimulates spermatogenesis
LSH and FSH are regulated by…
GnRH
How does testosterone control LH and FSH production?
Negative feedback to hypothalamus
Primary disorder of testes
Abnormal testosterone synthesis
Secondary disorder of testes
Due to primary disorder of pituitary or hypothalamus causing abnormal testosterone synthesis
Testosterone
- Principle male sex hormone
- Mainly secreted by testes but also secreted lesser extent by adrenal glands and ovaries
- Facial/body hair, muscle dev, secondary male sex traits
Hyperandrogenemia
- Adult males, no visual symptoms
- Prepubertal males: precocious puberty due to hypothalamic tumors, congenital adrenal hyperplasia, testicular tumor
- Female kids: develop male 2° traits/virilization
Congenital adrenal hyperplasia (CAH)
- Caused by enzyme defect of 21-hydroxylase, which prevents cortisol production
- Increased blood levels of cortisol precursors 17-OHP and ACTH
- Too much ACTH stimulates diffuse enlargement of adrenal glands, posing greater risk for tumors
Hypoandrogenemia
- Adult males: impotence, loss of 2° sex traits
- Prepubertal males: delayed puberty
Primary hypoandrogenemia
Causes include tumors, infections, congenital disorders, Klinefelter syndrome
Secondary hypoandrogenemia
Causes include primary hypofunction disorders of pituitary or hypothalamus -> reduced LH and FSH
Klinefelter syndrome
XXY chromosomes
Semen analysis
- Analyzed within 30 min
- Measure pH
- Motility, sperm count/morphology/viability
Ovaries
- Part of hypothalamic-pituitary-gonadal axis
- Estrogens and progesterone exert negative feedback to control LH and FSH synthesis
Estrogen
- Secreted by ovarian follicles and placenta
- Secreted by lesser extent in adrenal glands/testes
- Three primary estrogens: estradiol-17beta, estrone, and estradiol
Estradiol
Principle estrogen synthesized by ovaries
Progesterone
Secreted by ovarian follicles, mainly by corpus luteum following ovulation and placenta during pregnancy to maintain uterus
Which hormone peaks during ovulation?
Estrogen
Which hormone peaks during luteal phase?
Progesterone
Hyperestrinism in females
- Precocious puberty: ovarian tumor, hypothalamic tumor, adrenal tumors,
- Infertility and irregular menses: polycystic ovaries, estrogen-producing ovarian tumors, disorders of the hypothalamus or pituitary
- Postmenopausal bleeding: cervical or endometrial carcinoma, estrogen-producing ovarian tumors, exogenous estrogen consumption
Hyperestrinism in males
Testicular atrophy and enlargement/development of breasts
Hypoestrinism
- Ovarian insufficiency
- Delayed puberty
- Amenorrhea (absence of menstruation) due to menopause, chemo, severe stress, intense athletic training, excessive weight loss
- Tuner syndrome
Tuner syndrome
Genetic defect in females: partial or complete loss of one of the two X chromosomes -> non-functioning ovaries. Exogenous estrogen canbe given to obtain 2° sex traits
Hyperprogesteronemia
Prevents menstrual cycle from happening
Hypoprogesteronemia
Causes infertility, fetal abortion
Polycystic ovary syndrome
Common disorder presents itself in several ways:
- infertility, hirsutism (excess facial hair), chronic anovulation, glucose intolerance, hyperlipidemia/dyslipidemia, and hypertension
