Carlos Shared "17 Endocrine" - 105 Picmonics
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17 Endocrine
Thyroid Embryology
- Thyroid diverticulum arises from floor of primitive pharynx and descends into neck. Connected to tongue by thyroglossal duct, which normally disappears but may persist as cysts or the pyramidal lobe of thyroid.
- Thyroid tissue and parafollicular cells (aka, C cells, produce Calcitonin) of the thyroid are derived from endoderm.
- Foramen cecum is normal remnant of thyroglossal duct.
- abnormalities
- The pyramidal lobe of thyroid.
- Thyroglossal duct cyst presents as an anterior midline neck mass that moves with swallowing or protrusion of the tongue (vs persistent cervical sinus leading to branchial cleft cyst in lateral neck).
- Most common ectopic thyroid tissue site is the tongue (lingual thyroid).
- Removal may result in hypothyroidism if it is the only thyroid tissue present.
Thyroid Gland
- Characteristics
- TSH Stimulates T3 and T4 Release
- Metabolism Regulation
- Blood Calcium Sensor
- Calcitonin Release
- Blood Calcium Decreases
- Bone Building
2 mins
Adrenal Gland (Basic)
- Characteristics
- Adrenal Cortex
- RAAS Stimulates Aldosterone
- CRF (CRH) acts on Anterior Pituitary Gland to Release ACTH
- Cortisol Released
- Androgens Released
- Adrenal Medulla
- Epinephrine & Norepinephrine
2 mins
Adrenal Gland (Advanced)
- Characteristics
- Adrenal Cortex
- Zona Glomerulosa
- Aldosterone
- Zona Fasciculata
- Cortisol
- Zona Reticularis
- Androgens
- Adrenal Medulla
- Chromaffin Cells
- Epinephrine & Norepinephrine
2 mins
Anterior Pituitary
- Characteristics
- Hypothalamic Control
- FLAT PeG Mnemonic
- Tropic Hormones
- Follicle-Stimulating Hormone (FSH)
- Lutenizing Hormone (LH)
- Adrenocorticotropic Hormone (ACTH)
- Thyroid-Stimulating Hormone (TSH)
- Direct Hormones
- Prolactin (PRL)
- Growth Hormone (GH)
2 mins
Posterior Pituitary
- Characteristics
- Neuroendocrine Reflex Stimulation (By Hypothalamus)
- Direct Hormones
- Vasopressin
- Increased Water Retention (In Kidneys)
- Oxytocin
- Increased Uterine Contraction
- Mammary Glands Contraction
2 mins
Hypothalamus
- Characteristics
- Anterior Pituitary Stimulated Through the Hypophyseal Portal
- GHRH
- GnRH
- TRH
- PIF
- CRF Released During Stress
- Posterior Pituitary Stimulated Through Neural Control
3 mins
Pancreas
- Characteristics
- Acinar Cells Release Digestive Enzymes
- Ductal Epithelial Cells Release Bicarbonate
- Islets of Langerhans
- Beta Cells Release Insulin
- Alpha Cells Release Glucagon
- Delta Cells Release Somatostatin
- Somatostatin Inhibits Alpha and Beta Cells
3 mins
Insulin General Overview
- Anabolic effects of insulin:
- Increased glucose transport in skeletal muscle and adipose tissue
- Increased glycogen synthesis and storage
- Increased triglyceride synthesis
- Increased Na+ retention (kidneys)
- Increased protein synthesis (muscles)
- Increased cellular uptake of K+ and amino acids
- Decreased glucagon release
- Decreased lipolysis in adipose tissue
- Unlike glucose, insulin does not cross placenta.
Insulin Transporters 308
- GLUT transporters are via facilitated diffusion
- Insulin-dependent glucose transporters
- GLUT-4: adipose tissue, striated muscle (exercise can also increase GLUT-4 expression)
- Insulin-independent transporters
- GLUT-1: RBCs, brain, cornea, placenta
- GLUT-2 (bidirectional): β islet cells, liver, kidney, small intestine
- GLUT-3: brain, placenta
- GLUT-5 (fructose): spermatocytes, GI tract
Insulin Synthesis and Release
- INSULIN SYNTHESIS
- Preproinsulin (synthesized in RER)
- Cleavage of “presignal”
- Proinsulin (stored in secretory granules)
- Cleavage of proinsulin
- Exocytosis of insulin and C-peptide equally
- Insulin and C-peptide are increased in insulinoma and sulfonylurea use, whereas exogenous insulin lacks C-peptide
- SOURCE
- Released from pancreatic β cells.
- RELEASE
- Glucose is the major regulator of insulin release
- Glucose enters β cells
- Increased ATP generated from glucose metabolism
- Closes K+ channels (target of sulfonylureas)
- Depolarizes β cell membrane
- Voltage-gated Ca2+ channels open leading to Ca2+ influx
- Stimulation of insulin exocytosis
Insulin-dependent glucose uptake
- Binds insulin receptors (tyrosine kinase activity )
- Inducing glucose uptake (carriermediated transport) into insulin-dependent tissue.
- And gene transcription (via RAS/MAP kinase)
Insulin Response - Oral Glucose vs IV Glucose
- Increased insulin response with oral vs IV glucose because of incretins such as glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which are released after meals and increased β cell sensitivity to glucose.
Glucagon (GlucaGen)
- Mechanism
- Increases Glucose
- Indications
- Hypoglycemic Emergency
- Side Effects
- Nausea and Vomiting
- Considerations
- Reconstitute Powder
- Consume Oral Carbohydrates
- 50% Dextrose IV (If No Effect)
2 mins
Hypothalamic-pituitary hormones
- CRH
- Increases ACTH, MSH, β-endorphin
- Decreased in chronic exogenous steroid use.
- Dopamine
- Decrease prolactin, TSH
- Dopamine antagonists (eg, antipsychotics) can cause galactorrhea due to hyperprolactinemia
- GHRH
- Increase GH
- Analog (tesamorelin) used to treat HIV-associated lipodystrophy.
- GnRH
- Increases FSH, LH
- Suppressed by hyperprolactinemia.
- Tonic GnRH suppresses HPG axis (Hypothalamic–pituitary–gonadal axis)
- Pulsatile GnRH leads to puberty, fertility.
- Prolactin
- Decreases GnRH
- Pituitary prolactinoma leads to amenorrhea, osteoporosis, hypogonadism, galactorrhea.
- Somatostatin
- Decreases GH, TSH
- Analogs used to treat acromegaly.
- TRH
- Increase TSH, prolactin
- Increased TRH (eg, in 1°/2° hypothyroidism) may increase prolactin secretion, leading to galactorrhea.
Prolactin Regulation
Growth hormone (somatotropin)
- SOURCE
- Secreted by anterior pituitary
- FUNCTION
- Stimulates linear growth and muscle mass through IGF-1 (Insulin-like Growth Factor/somatomedin C) secretion by liver.
- Increased insulin resistance (diabetogenic).
- REGULATION
- Released in pulses in response to growth hormone–releasing hormone (GHRH).
- Secretion increases during exercise, deep sleep, puberty, hypoglycemia. Arginine stimulates release.
- Secretion inhibited by glucose and somatostatin release via negative feedback by somatomedin.
- Excess secretion of GH (eg, pituitary adenoma) may cause acromegaly (adults) or gigantism (children).
- Treat with somatostatin analogs (eg, octreotide) or surgery.
Appetite regulation
- Ghrelin
- Stimulates hunger (orexigenic effect) and GH release (via GH secretagog receptor).
- Produced by stomach.
- Sleep deprivation or Prader-Willi syndrome leads to increased ghrelin production
- Decreases after gastric bypass surgery.
- Lateral area of the hypothalamus is stimulated by ghrelin
- Leptin
- Satiety hormone.
- Produced by adipose tissue.
- Mutation of leptin gene leads to congenital obesity.
- Sleep deprivation or starvation leads to decreased leptin production.
- Ventromedial area of the hypothalamus is stimulated by Leptin
- Endocannabinoids
- Act at cannabinoid receptors in hypothalamus and nucleus accumbens, two key brain areas for the homeostatic and hedonic control of food intake.
- Causes increased appetite.
- Exogenous cannabinoids cause “the munchies.”
17 Alpha Hydroxylase Deficiency
- Decreased Cortisol
- Decreased Sex Hormones
- Increased Mineralocorticoids (DOC)
- Hypertension
- Hypokalemia
- XY Externally Phenotypic Female
- No Internal Reproductive Structures Due to Mullerian Inhibitory Factor
- XX Externally Phenotypic Female
- Sexual Infantilism
2 mins
21 Hydroxylase Deficiency
- Pathophysiology
- Decreased Cortisol
- Increased 17 Hydroxyprogesterone
- Decreased Aldosterone
- Signs and Symptoms
- Hypotension
- Increased Renin
- Hyperkalemia
- Female Pseudohermaphroditism
2 mins
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