DIT review - Endocrinology 1 Flashcards
Which hormones use the cAMP pathway (Gs and Gi)
- Most hormones of anterior pituitary
- FSH, LH, ACTH, TSH, hCG, MSH, GHRH, CRH, PTH, calcitonin, glucagon, V2 vasopressin receptor
Which hormones use IP3 pathway (Gq)
- Hormones of posterior pituitary minus V2
- GnRH, TRH, oxytocin, V1 vasopressin receptor, H1 histamine receptor, angiotensin II, gastrin
Which hormones use cGMP pathway
- Vasodilators
- Nitric oxide (NO), Atrial natriuretic peptide (ANP)
Which hormones use steroid receptors
Estrogens, progesterone, testosterone, glucocorticoids, aldosterone, thyroid hormone (T3/T4), vitamin D
Which hormones use tyrosine kinase receptors
- Insulin, insulin-like growth factor (IGF-1), platelet derived growth factor (PDGF), fibroblast growth factor (FGF)
Which hormones use nonreceptor tyrosine kinase (e.g. JAK/STAT)
- Prolactin, cytokines (IL-2, IL-6, IFN), GH, G-CSF, Erythropoietin, Thrombopoeitin
Causes of hyperprolactinemia
- Pregnancy/nipple stimulation
- Stress
- Prolactinoma
- Dopamine antagonists
Presentation of hyperprolactinemia
- Due to prolactin’s inhibitory effects on GnRh
- Premenopausal women:
- Hypogonadism, infertility, oligo/amenorrhea, galactorrhea (rare)
- Postmenopausal women:
- Asymptomatic
- Males:
- Hypogonadism, decreased libido, impotence, infertility, gynecomastia, galactorrhea (rare)
Effects of growth hormone on insuline
- Increases insulin resistance (diabetogenic)
How do you diagnose acromegaly?
Increased serum IGF-1
Growth hormone is secreted in a pulsatile fashion and levels fluctuate throughout the day by IGF-1 levels are generally consistent
Confirmatory test - failure to suppress serum GH following oral glucose tolerance test
What disorder is characterized by failure to breast-feed, absent menstruation, and cold intolerance after giving birth
Sheehan Syndrome - ischemic infarct of pituitary following postpartum bleeding
Draw out the steroid synthesis pathway, including enzymes
Describe the main features of each of the congenital adrenal hyperplasia enzyme deficiencies (21 a-hydroxylase, 17 a-hydroxylase, 11 b-hydroxylase)
- HINTS:
- If there is a 1 in the first digit of deficient enzyme (11 or 17) – will be HTN
- If there is a 1 in the second digit of deficient enzyme (11 or 21) – will be masculinization
- K+ does the opposite of whatever Na+ does
- 21 a-hydroxylase
- Hypotension
- Hyperkalemia
- Masculinization
- 11 b-hydroxylase
- Hypertension
- Hypokalemia
- Masculinization
- 17 a-hydroxylase
- Hypertension
- Hypokalemia
- Ambigious genitalia in XY
- Lack of secondary sexual development in XX
What are the actions/effects of cortisol
- Increased BP
- Upregulates a1 receptors in arterioles, thus increasing sensitivity to NE and Epi
- Increases insulin resistance (diabetogenic)
- Increases gluconeogenesis, lipolysis, proteolysis
- Decreases fibroblast activity (skin thinning and striae)
- Decreases inflammatory and immune response
- Will initially see neutrophilia due to decreased WBC adhesion
- Decreases bone formation
Causes of Cushing syndrome
- Exogenous corticosteroids (most common cause)
- ACTH-secreting pituitary adenoma (Cushing disease)
- Paraneoplastic ACTH secretion (e.g. small cell lung cancer)
Describe how a Dexamethasone suppression test helps to differentiate between different causes of Cushing syndrome
- First give low-dose dexamethasone (synthetic glucocorticoid)
- Measure ACTH:
- If low, suspect adrenal tumor or exogenous glucocorticoids
- If high, suspect Cushing disease (ACTH-pituitary adenoma) or ectopic ACTH secreting tumor
- Give high dose Dexamethasone:
- Cortisol levels will decrease if Cushing Disease
- Cortisol levels will remain elevated if ectopic tumor
- Give high dose Dexamethasone:
What is the effect of glucocorticoids on bones?
Osteoporosis
Chronic glucocorticoid use should be supplemented with calcium and/or vitamin D
What is the most common cause of primary adrenal insufficiency
Aka Addison disease
Most commonly due to autoimmune destruction of adrenal gland
Presentation of primary adrenal insufficiency
o Lack of cortisol - Weakness, fatigue, weight loss
o Lack of aldosterone - hypotension, hyponatremia, hyperkalemia
o Increased ACTH - skin hyperpigmentation (due to POMC)
Cause of acute primary adrenal insufficiency
Waterhouse-Friederichsen syndrome
Acute primary adrenal insufficiency due to adrenal hemorrhage associated with septicemia (usually Neisseria meningitides), DIC, endotoxic shock
What is the presentation of secondary adrenal insufficiency
o Lack of cortisol due to decreased ACTH à weakness, fatigue, weight loss
o Aldosterone synthesis is preserved (controlled by RAAS) à no hypotension or hyperkalemia
o ACTH low à no hyperpigmentation
What is the most common cause of tertiary adrenal insufficiency
Usually caused by abrupt withdrawal of exogenous steroids after chronic usage
What is Conn syndrome
Primary hyperaldosteronism due to adrenal adenoma
What is the classic presentation of hyperaldosteronism
· Hypertension
· Hypokalemia
· Metabolic alkalosis
