Endocrine System Review Flashcards
Hypoglycemia
- Definition
- Level 1 & 2
- S/s
Blood glucose <50 mg/dL
- More common in people with DM1 (only 5-10% is type 1; average of 2 episodes/week)
- If severe hypoglycemia is uncorrected → coma and/or death
- Nondiabetic hypoglycemia is rare and is either reactive (diet related) or fasting (diseae related)
Level 1 hypoglycemia: glucose alert as fasting BG (FBS) of ≤70 mg/dL
Level 2: BG ≤54 mg/dL
- This low BG indicates serious, clinically important hypoglycemia
Signs & Symptoms
- weakness
- hand tremors
- anxiety
- feels like passing out
- difficulty concentrating
- irritability
Overview: Type 1 DM
1. Definition/ Etiology
2. S/s
3. Labs
4. Complications
- School-age child w/ recent onset of persistent thirst (polydipsia), frequent urination (polyuria), and weight loss
- Diagnosis peaks at ages 4-6 and again from ages 10-14 years
- School-age child w/ recent onset of persistent thirst (polydipsia), frequent urination (polyuria), and weight loss
- feeling of hunger even though eating an ↑ amount of food; weight loss
- polydipsia
- polyuria
- blurred vision (osmotic effect on lens)
- “fruity” odor breath
- may report recent viral-like illness before onset of symptoms
- feeling of hunger even though eating an ↑ amount of food; weight loss
- large # of ketones in urine
- Diabetic Ketoacidosis (DKA) + neurologic symptoms (drowsiness, lethargy, can progress to coma)
Overview: Thyroid Cancer
1. Definition/ Etiology
2. S/s
- A single thyroid nodules, usually located on upper half of one lobe
- may be accompanied by enlarged cervical lymph node lump, swelling, or pain
- higher incidence in Asian race
- Radiation therapy during childhood for certain cancers (Wilm’s tumor, lymphoma, neuroblastoma) and/or a low-iodine diet ↑ risks
- higher prevalence in women (3:1)
- highest incidence from 20-55 years
- Positive family hx of thyroid cancer
- metastasis is by lymph route - c/o hoarseness, problems w/ swallowing (dysphagia, dyspnea, or cough)
Overview: Pheochromocytoma
1. Definition/ Etiology
2. S/s
- rare hormone-releasing adrenal tumor
- generally occurs in persons age 20-50 but can appear at any age
- episode resolve spontaneously
- in b/w attacks, VSS normal
- Triggers: physical exertion, anxiety, stress, surgery, anesthesia, changes in body position, labor & delivery, or foods high in tyramine (some cheeses, beers, wines, chocolates, dried or smoked meats) + MAOIs and stimulant drugs are other triggers - random episodes of headache (mild - severe)
- diaphoresis
- tachycardia
- hypertension
- random episodes of headache (mild - severe)
Overview: Hyperprolactinemia
1. Definition/ Etiology
2. S/s
3. Labs
4. Complications
- can be a sign of pituitary adenoma
- slow onset
- women may present w/ amenorrhea
- galactorrhea in both males and females
- can be a sign of pituitary adenoma
- when tumor is large enough to cause a mass effect → headaches and vision changes
- serum prolactin ↑
Endocrine System: Normal Findings
- Endocrine system works as a “negative feedback” system
- If lower level of “active’ hormones → stimulates production.
- inversely, if level of hormones is high → stops production
- Hypothalamus stimulates the anterior pituitary gland into producing the stimulation hormones (follicle-stimulating [FSH], luteinizing hormone [LH], thyroid-stimulating hormone [thyrotropin; TSH])
- These stimulating hormones tell target orangs (e.g., ovaries, thyroid) to produce “active” hormones (e.g., estrogen, thyroid hormone)
- High level of these “active’ hormones work in reverse → the hypothalamus directs the anterior pituitary into stopping production of the stimulating hormones (e.g., TSH, LH, FSH)
Endocrine Glands: These glands interact to form the HPA axis
HPA axis: hypothalamic-pituitary-adrenal axis
Hypothalamus: TRH, GnRH, CRH, GHRH, Somatostatin
“On or Off” Switches → (for target organs)
Anterior Pituitary: TSH, FSH, TH, GH, ACTH, NSH, Prolactin
Posterior Pituitary: Antidiuretic hormone and oxytocin
Target Organs
- Thyroid (TSH): T3 and T4
- Ovaries/Testes (FSH/LH): estrogen, propgesterone, androgens, testosterone
- Adrenal cortex (ACTH): glucocorticoids, mineralocorticoids
- Body (GH): somatic growth
- Uterus (oxytocin): uterine contractions, bonding
- Kidneys (vasopressin): blood volume
- Pineal (melatonin): circadian rhythm
- Breast (prolactin): milk production
Hypothalamus function
Coordinates the nervous and endocrine system by sending signals via pituitary gland; gland interacts to form the HPA axis; produces neurohormones that stimulate or stop production of pituitary hormones
Pituitary Gland function
Located at sella turcica (base of the brain)
- stimulated by hypothalamus into producing the stimulating hormones such as FSH, LG, TSH, adrenocorticotropic hormone (ACTH), and growth hormone (GH)
Anterior Pituitary Gland function
Adenohypophysis
- Has two lobes (anterior and posterior)
- The anterior pituitary gland produces hormones that directly regular the target organs (e.g., ovaries, testes, thyroid, adrenals)
Posterior Pituitary Gland function
Secretes antidiuretic hormone (vasopressin) and oxytocin, which are made by the hypothalamus but stored an secreted by the posterior pituitary
FSH
Follicle-stimulating hormone
- stimulations the ovaries to enable growth of follicles (or eggs)
- production of estrogen
LH
Luteinizing hormone
- Stimulates the ovaries to ovulate
- Production of progesterone (by corpus luteum)
- In males, LH stimulates the testicles (Leydig cells) to produce testosterone
TSH
Thyroid-stimulation hormone
- stimulates thyroid gland
- production of triiodothyronine (T3) and thyroxine (T4)
GH
Growth hormone
- stimulates somatic growth of the body
ACTH
Adrenocorticotropic hormone
- Stimulates the adrenal glands (two portions of the gland: medulla and cortex)
- Production of glucocorticoids (cortisol) and mineralocorticoids (aldosterone)
Prolactin
- affects lactation and milk production
Melanocyte-stimulating hormone
- Production of melatonin in response to UV light; highest levels at night b/t 11pm and 3am
Thyroid Gland function
A butterfly-shaped orang (two lobes) located below the prominence of the thyroid cartilage (Adam’s apple)
- 2 inches long, and loves are connected by the isthmus
- uses iodine to produce T3 and T4
Parathyroid Glands function
- Locate behind the thyroid glands (two glands behind each lobe)
- produces parathyroid hormone (PTH), responsible for calcium balance of the body by regulating the calcium loss or gain from the bones, kidneys, and GI tract (calcium absorption)
Pineal Gland function
Pea-sized gland located inside brain that produces melatonin, which regulates sleep-wake cycle
- darkness stimulates melatonin production and light suppresses it
Primary Hyperthyroidism
1. Definition/Etiology
2. Clinical Presentation
3. Objective Finding
AKA Thyrotoxicosis
1. - Classic finding is very low (or undetectable) TSH with ↑ in both serum free T4 and T3 levels
- most common cause for hyperthyroidism (60-80%) in US
- chronic autoimmune disorder → Graves’ disease
- middle-aged woman loses a large amount of weight rapidly
- anxiety
- insomnia
- cardiac symptoms (d/t overstimulation); palpitations
- hypertension
- atrial fibrillation
- premature atrial contractions
- warm and moist skin with ↑ perspiration
- may present w/ ophthalmopathy and lid lag (Graves’ ophthalmopathy)
- More frequent BMs (looser stools)
- Amenorrhea
- Heat intolerance
- Enlarged thyroid (goiter) and/or thyroid nodules present
- May be accompanied by pretibial myxedema (thickening of skin usually located in shins and gives an orange-peel appearance)
- middle-aged woman loses a large amount of weight rapidly
- Thyroid: Diffusely enlarged gland (goiter), toxic adenoma, or multinodular goiter; may be tender to palpation or asymptomatic
- Extremities: Fine tremors in both hands, sweaty palms, pretibial myxedema
- Eyes: Lid lag; exophthalmos in one or both eyes
- Cardiac: Tachycardia, atrial fibrillation, CHF, cardiomyopathy
- Integumentary: Fine hair, warm skin
- Neurologic: Brisk deep tendon reflexes
- Thyroid: Diffusely enlarged gland (goiter), toxic adenoma, or multinodular goiter; may be tender to palpation or asymptomatic
Graves’ Disease
Accounts for 60-80% of all types of hyperthyroidism
- An autoimmune disorder causing hyperfunction and production of excess thyroid hormones (T3 and T4).
- Higher incidence in women (7:1); these women are also at higher risk for other autoimmune diseases such as RA and pernicious anemia and for osteopenia/osteoporosis d/t ↑ metabolism
Primary Hyperthyroidism
4. Labs
- Very low TSH (<0.05 mU/L) w/ ↑ T4 and T3
- If Graves’ disease → positive thyrotropin receptor antibodies (TRAb), aka thyroid-stimulation immunoglobulins (TSIs)
- Thyroid peroxidase antibody (TPO) is positive with Graves’ disease as well as Hashimoto’s disease
- Very low TSH (<0.05 mU/L) w/ ↑ T4 and T3
WORK UP:
- Check TSH → If low, order thyroid panel
* Look for very low TSH (<0.05 mU/L) w/ ↑ T3 and T4
- In some pts w/ very low TSH, only either the T4 or T3 will be elevated
- Next step → order antibody tests to confirm whether Graves’ disease is present (TRAb and TPO or TSI)
- If thyroid has a single palpable mass/nodule → order thyroid ultrasound → Refer to endocrinologist for management
Imaging:
- Thyroid ultrasound, 24-hr radioactive iodine uptake (RAIU) shows diffuse uptake (goiter)
- If solitary toxic nodule, shows warm or “hot” nodule or “cold” nodule
- Absolute contraindications for this test: Pregnancy and Breastfeeding
Primary Hyperthyroidism
5. Treatment (Meds + Adjunctive)
Medications:
- Methimazole (Tapazole) → shrinks thyroid gland/↓ hormone production
- Propylthiouracil (PTU) → shrinks thyroid gland/↓ hormone production; PTU is preferred treatment for mod-severe hyperthyroidism (can cause liver failure)
Side effects:
- Skin rash
- granulocytopenia/aplastic anemia
- thrombocytopenia (check CBC w/ platelets)
- hepatic necrosis (monitor CBC, LFTs)
Pregnancy → For hyperthyroidism, PTU is preferred treatment if needed. For high-risk pregnancy → Refer to obstetrician
Adjunctive Treatment: Given to alleviate symptoms of hyperstimulation (e.g., anxiety, tachycardia, palpitations)
- Beta-blockers are effective (e.g., propranolol, metoprolol, atenolol)
Radioactive Iodine: Permanent destruction of thyroid gland resulting in hypothyroidism for life (needs thyroid supplementation for life)
- CONTRAINDICATION: Pregnancy or lactation
- Alternative/natural medication (controversial): Armour thyroid is produced from desiccated (dried) pig thyroid glands (contains both T3 and T4)
** Some practitioner chooses to prescribe this - Drug-induced thyroid disease: Lithium, amiodarone, high dose of iodine, interferon alfa, dopamine. → Monitor TSH
** ALL hyperthyroid patients should be referred to an endocrinologist ASAP!
Primary Hyperthyroidism
6. Complications
- Thyroid Storm (thyrotoxicosis) → During thyroid storm, an individual’s heart rate, BP, and body temp can soar to dangerously high levels
- Acute worsening of symptoms d/t stress or infection
- Look for ↓ LOC, fever, abdominal pain
- Life-threatening! → Immediate hospitalization!
** People w/ subclinical and overt hyperthyroidism are at ↑ risk of bone (osteopenia/osteoporosis) and cardiac (afib) complications
** If new onset of Afib, check TSH; Keep TSH between 1.0-4.0 mU/L as goal for thyroid hormone supplementation
Thyroid Gland Tests
- Thyroid gland ultrasound: Used to detect goiter (generalized enlargement of gland), multinodular goiter, single nodule, and solid versus cystic masses
- Fine-needle biopsy: Diagnostic test for thyroid cancer
- Thyroid Scan (24-hr thyroid scan w/ RAIU): shows metabolic activity of thyroid gland
- Cold spot: Not metabolically active (more worrisome; r/o thyroid cancer); fine-needle aspiration biopsy
- Hot spot: Metabolically active nodule with homogenous uptake; usually benign; helpful in diagnosing recurrent disease
Laboratory Findings of Thyroid Disease
TSH
- Normal range: 0.5 - 5.0 mU/L (third-generation test)
- TSH is used for both screening and monitoring response to treatment
- Recheck TSH Q6-8 weeks
- Dose of levothyroxine (Synthroid) is based on the TSH level
- Goal is TSH <5.0 mU/L
- When TSH is stable, recheck Q6-12 months
Primary Hypothyroidism
1. Definition/Etiology
2. Clinical Presentation
3. Labs
4. Treatment
- high TSh w/ low free T4 levels (do not confuse w/ total T4)
- Diagnosis is based on the lab findings
Common causes:
- Hashimoto’s thyroiditis (most common cause)
- postpartum thyroiditis
- thyroid ablation w/ radioactive iodine
- middle-aged-to-older woman, overweight c/o:
- fatigue
- weight gain
- cold intolerance
- constipation
- menstrual abnormalities
- may have alopecia on outer 1/3 of both eyebrows
- serum cholesterol ↑
- may have hx of another autoimmune disorder (e.g., RA, PA)
- Alopecia of outer 1/3 eyebrow and myxedema os symptoms of hypothyroidism
- middle-aged-to-older woman, overweight c/o:
- TSH (TSH >5.0 mU/L) → if ↑, order TSH w/ free T4N (free thyroxine)
- If TSH ↑ and serum-free T4 is ↓ = hypothyroidism
- Next step: order TPOs to confirm Hashimoto’s thyroiditis
- If TPOs ↑ = confirms Hashimoto’s thyroiditis (GOLD STANDARD for diagnosing Hashimoto’s)
- TSH (TSH >5.0 mU/L) → if ↑, order TSH w/ free T4N (free thyroxine)
- Starting dose of levothyroxine (Synthroid) ranges from 25-50 mcg/day
- Start w/ lowest dose for older adults/pt with hx of heart disease (watch for angina, acute MI, atrial fibrillation)
** Advise pt to crush Synthroid tablets w/ teeth before swallowing w/ water for better absorption; these tablets are synthetic T4 (levothyroxine)
- Starting dose of levothyroxine (Synthroid) ranges from 25-50 mcg/day
- ↑ Synthroid dose every few weeks until TSH is normalized (TSH <5.0 mU/L)
- Recheck TSH Q6-8 weeks until TSH normal. When under control, check TSH Q12 months - If TSH is 0.05 - 5.0 mU/L → WNL, pt is at right dose of Synthroid
- Do not check earlier than 6 weeks
- Advise pt to report if palpitations, nervousness, or tremors → means that Synthroid dose is too high (↓ dose until symptoms are gone and TSH is normal)
** Chronic amenorrhea and hypermetabolism → osteoporosis. Supplement w/ calcium and w/ Vit D 1,000 mg; engage in weight-bearing exercises
Hashimoto’s Thyroiditis
A chronic autoimmune disorder of the thyroid gland
- generally no pain w/ this thyroid swelling
- body produces destructive antibodies (TPOs) against they thyroid gland that gradually destroys them
- almost all pt (90%) w/ Hashimoto’s → elevated TPOs
- most develops goiter
- more common in women, 8:1
