PGY 412 Endocrinology and Neurology

Prevalence

long term accumulation of all existing cases of a disease, condition, or trait; reports how common a condition is

Incidence

short term accumulation of all new cases of a disease, condition, or trait; reports the risk of getting a condition

Negative Feedback

also known as pumping the brakes; a regulatory mechanism to counteract hormone response to maintain balance throughout an organism

Hormone

chemical released from a specialized tissue into the bloodstream to convey regulatory information to target organs of the body

Steroid Hormones

lipid soluble, diffuse across the plasma membrane, long lasting response, bound to carriers in the bloodstream, and cell signaling coupled to gene expression

Peptide Hormones

bind to cell surface receptors, short acting response, easily degraded in the bloodstream, move freely, and cell signaling is generally transient

Diurnal

24 hour secretion cycle

Pulsatile

secretion cycle where a burst is a followed by a lag

Infradian

patterns of secretion that last more than one day (like a menstrual cycle)

Blood Test

can measure hormone levels as well as specific salts and minerals

Dynamic Test

challenging the system with a bolus to observe how the endocrine system responds

Hypothalamus

the brain region that is directly coupled to the endocrine system via the pituitary

Posterior Pituitary

hormones are stored in the axon terminals until a stimulus promotes release into the bloodstream

Anterior Pituitary

neuro-secretory cells of the hypothalamus release specific hormones that stimulate the release of this gland’s tropic hormones

Prolactin (Pr)

AP; stimulates milk production

Growth Hormone (GH)

AP; regulates growth in children and blood glucose levels

Adrenocorticotropin (ACTH)

AP; stimulates the production of cortisol

Thyroid Stimulating Hormone (TSH)

AP; stimulates the thyroid gland

Luteinizing Hormone (LH)

AP; regulates testosterone and estrogen

Follicle-Stimulating Hormone (FSH)

AP; stimulates testis and ovaries

Oxytocin

PP: uterus contraction and milk ejection

Antidiuretic Hormone (ADH)

PP: regulates water balance

Function of ADH

promotes reabsorption of water

ADH Target Organ

collecting ducts of the kidneys

ADH Stimulus

high osmolality (high blood sodium concentration)

Syndrome of Inappropriate ADH Secretion (SIADH)

unsuppressed release if ADH from the pituitary gland or non-pituitary sources (common in geriatric patients); basically unchecked levels of ADH

SIADH Risk Factors

hypoatremia (low sodium levels in the blood), certain medications

SIADH Symptoms

nausea, vomiting, confusion, fatigue, seizures

Causes of SIADH Pathology

hyperactive stimulus sensing at the hypothalamus, small cell carcinoma secretion of ADH at the level of the pituitary/lung, increased ADH sensitivity at the level of the kidney; rarer: strokes near the hypothalamus/pituitary

Medications that can Increase SIADH Risk

anti-seizure drugs, antidepressants, cancer medication, heart meds, diabetes meds, and blood pressure meds

Iatrogenic

illness caused by medical examination or treatment

Lab Workup Red Flags for SIADH

low serum sodium, higher sodium levels in urine

Non-acute Case Treatment for SIADH

fluid restriction

Extreme Case Treatment for SIADH

IV hypertonic saline

Iatrogenic Case Treatment for SIADH

adjustment to medications

Parathyroid Glands

release PTH in response to low blood calcium levels

Tissues and Functions Sensitive to Calcium Levels

heart, brain, muscles, secretory cells, blood clotting, and cellular metabolism

Hypercalcemia

leads to kidney stones, constipation, confusion, and fatigue

Proper Gut/Kidney Function

required to maintain blood calcium levels

Resorption

osteoclasts break down bone to release calcium into the blood

Deposition

osteoblasts sequester calcium into bone

Osteoporosis

a condition of depleted and decreased bone density where bones are fragile and more likely to break

Osteoporosis Diagnosis

after a fall or sudden impact causes a bone to fracture; spontaneous bone fracture

Pathological Break

a bone fracture did not occur due to an outside force or stress

Osteoporosis Risk Factors

hyperparathyroidism, malabsorption of nutrients, anorexia, hyperthyroidism, chronic renal failure, crushing syndrome, any disease that can lead to ling term immobilization, vit D deficiency, living with diabetes, and a history of breast cancer; tose who have lost greater than one inch of height

Osteoporosis Symptoms

back pain, stooped posture, loss of height over time, bones breaking easily

Osteoporosis Pathology

the balance between bone resorption and bone deposition is disrupted, leading to excessive resorption and weakened bones

Osteoporosis Diagnosis

bone mineral density test is performed (DXA) of the hip and the spine; low BMD (more porous) is the defining characteristic

DXA Scan

duel-energy X-ray absorptiometry scan

Osteoporosis Treatment

dietary supplement, medication (bisphosphonates), lifestyle changes (limiting alcohol consumption and caffeine)

Osteoporosis Prevention

quit smoking, weight bearing exercises, resistance exercises, calcium/vit D supplements

Thyroid Hormone

increases cellular metabolism by raising the body’s basal metabolic rate

BMR

the minimum number of calories your body needs to perform basic, life sustaining functions at rest

Cellular Metabolism

the total set of life sustaining chemical reactions that happen inside living cells

Catabolism

breaks down large molecules (like nutrients or food) into smaller parts; this process releases energy which the cell captures as ATP

Anabolism

uses energy and small building blocks to construct large, complex molecules thta the cell needs to grow and repair itself

Thyroid Gland

traps and transforms iodine in order to make and release T3 and T4

Hypothalamus Role in Thyroid Endocrinology

secretes TRH to stimulate the anterior pituitary

Anterior Pituitary Role in Thyroid Endocrinology

secretes TSH to stimulate thyroid cells to release T4 and T3

T3 and T4 Negative Feedback

bind to receptors at the level of the pituitary to inhibit TSH release; inhibit release of TRH at the level of the hypothalamus

Stimulators of the Hypothalamus to Release TRH

cold temperature, stress, exercise, low blood glucose

Actions of Thyroid Hormones at the Level of the Body

increase BMR, increase oxygen consumption, essential for normal growth, mental development, sexual maturation, increase heart rate by increasing the sensitivity of tat cardiovascular system of catecholamines

Goiter

thyroid enlargement, hypo or hyper function

Adenoma

a non-cancerous tumor the begins in gland like cells of the epithelial tissue; can develop in various organs (pituitary, liver adrenal glands, and parathyroid glands); often asymptomatic but can lead to health issues by producing excess hormones or by pressing on nearby structures

Hypothyroidism Prevalence

ranges from 2-15% of the population; female to male ratio of 10:1, increases with age, mean diagnosis is 60 years

Causes of Hypothyroidism Pathology

iodine deficiency; autoimmune disease (hashimoto’s); iatrogenic causes

Hypothyroidism Risk Factors

worldwide, areas of iodine deficiencies, genetic, treatment for hyperthyroidism

Hypothyroidism Symptoms

lethargy, weight gain, sensitivity to cold, dry skin and hair, slow heart rate, swelling

Hypothyroidism Pathology

insufficient thyroid hormone production; pathology is secondary, resulting from disruptions of the hypothalamus or pituitary gland

Hypothyroidism Treatment

replacement therapy, administer thyroxine (T4)

Hypothyroidism Diagnostic Tool

test for the presence of autoimmune antibodies against TPO

TPO

thyroid peroxidase; an enzyme essential for the production of thyroid hormones

When T4 Treatment is Used

mild TPOAb+ hypothyroidism and primary/autoimmune TPOAb+ hypothyroidism

Hypothyroidism Hormone Levels

TSH is high; T3.T4 are low

Thyroid Hormones - Negative Feedback

T3 and T4 bind to receptors at the level of the pituitary and inhibit the release of TSH (short loop); T4 and T3 also inhibit the release of TRH at the level of the hypothalamus

Hyperthyroidism

over activity of the thyroid gland, with resultant excessive secretion of thyroid hormones and accelerated metabolism in the periphery

Thyrotoxicosis

condition that results from any cause of increased thyroid hormone levels, and can be caused by dysfunction of the pituitary, thyroid gland, ectopic thyroid tissue, or the ingestion of excessive amounts of thyroid hormone medication; the clinical effects of unbound thyroid hormone

Primary Hyperthyroidism

results directly from thyroid gland disruption

Central/Secondary Hyperthyroidism

less common and typically results from TSH-secreting pituitary adenomas

Hyperthyroidism Prevalence

higher female prevalence (2%) compared to males (0.2%)

Hyperthyroidism Causes of Pathology

autoimmune disease (Grave’s disease), toxic multinodular goiter (TMNG), toxic adenoma, iatrogenic, conditions associated with high HGC levels arising from certain types of tumors (less common)

Hyperthyroidism Risk Factors

family history of thyroid disease, particularly grave’s disease, chronic illnesses (including pernicious anemia and primary adrenal insufficiency), recent pregnancy

Hyperthyroidism Symptoms

thin hair, enlarged thyroid, fast heart rate, weight loss, warm skin, and heat tolerance

Hyperthyroidism Pathology

too much thyroid hormone, T3, and T4

Hyperthyroidism Treatment

medication to block production of thyroid hormones, radioactive iodine to destroy thyroid cells, thyroidectomy

Hyperthyroidism Hormone Levels

TSH low; T3/T4 high

Goiter

swelling in the neck resulting from enlarged thyroid gland; over 90% of cases are caused by iodine deficiency; most are benign in nature; approximately 800 million people subsist on an iodine-deficient diet

Uninodular Goiter

one thyroid nodule; can be either an inactive or a toxic nodule

Multinodular Goiter

multiple nodules; can be inactive or toxic, the latter is associated with hyperthyroidism

Diffuse Goiter

the whole thyroid appearing to be enlarged due to hyperplasia (increase in number of cells in an organ or tissue)

Estrogen

promotes the maturation of ovarian follicles

Key Steps of the Menstrual Cycle

follicles develop, and one matures, suppressing the others from continuing to mature; ovulation occurs; the corpus luteum forms and secretes factors that prepare uterine lining to thicken and become receptive to a fertilized egg

Ovulation

direct result of a surge in the pituitary hormones LH and FSH

Follicular Phase

characterized by menstrual bleeding at the beginning and the LH and FSH serge at the end (~14 days)

Luteal Phase

initiated by rupture of a mature follicle and release of an egg/ovulation; surge in progesterone and uterine thickness (~14 days)

HCG (Human Chorionic Gonadotropin)

necessary to maintain early pregnancy and is detectible by urine pregnancy test

HCG Complications

levels can become high enough to increase thyroid hormone production at the level of the thyroid gland; complications resulting are rare, and normally more than one measurement is taken to diagnose

Female Reproduction Negative Feedback - Hypothalamic Level

estrogen suppresses the release of GnRH

Female Reproduction Negative Feedback - Pituitary Level

estrogen suppresses the release of LH and FSH

LH and FSH

work together to stimulate the ovaries to produce estrogen