Endocrine

1. Endocrine System BasicsPurpose

• Maintains internal homeostasis

• Integrates the body's response to the external environment

• Works closely with the nervous system

Endocrine vs. Exocrine

Endocrine

• Hormones released directly into bloodstream

• No ducts

• Hormones act as chemical messengers

Exocrine

• Secretions travel through ducts

Major Endocrine Glands

• Hypothalamus

• Pituitary

• Thyroid

• Parathyroid

• Adrenal glands

• Pancreas

• Ovaries

• Testes

2. HormonesHormones

Produced in tiny amounts but have powerful effects.

Functions

• Regulate metabolism

• Growth & development

• Tissue function

• Sexual function

• Reproduction

• Sleep

• Mood

Exam Tip: Hormones are broken down immediately after they are used.

3. Hypothalamus (MASTER Gland ⭐)Main Functions

• Maintains homeostasis

• Detects changes in blood chemistry

• Responds to internal and external stimuli

• Controls the pituitary gland

Neurocenters regulate:

• Temperature

• Hunger

• Thirst

• Emotions

• Thoughts

Releasing Hormones

Purpose: Turn hormone production ON

Hypothalamus
⬇
Releasing Hormone
⬇
Pituitary
⬇
Target gland
⬇
Hormone produced

Examples:

• CRH

• TRH

Inhibiting Factors

Purpose:

• Shut hormone production OFF

• Prevent excessive hormone levels

Easy Memory Trick

Releasing = ON

Inhibiting = OFF

4. Pituitary GlandThree LobesAnterior Pituitary

Produces 6 major hormones

Functions:

• Growth

• Reproduction

• Metabolism

Hormones released in a diurnal rhythm

• Peak secretion depends on time of day

• Influenced by sleep and exercise

Posterior Pituitary

Stores:

• ADH (vasopressin)

• Oxytocin

ADH

• Retains sodium & water

• Released when blood volume decreases

Oxytocin

• Uterine contractions

• Milk let-down

Intermediate Lobe

Produces:

• Endorphins

• Enkephalins

Functions:

• Pain control

• Stress response

5. Negative Feedback (VERY HIGH-YIELD ⭐⭐⭐⭐⭐)

Think of it like supply and demand.

Low hormone
⬇
Hypothalamus releases releasing hormone
⬇
Pituitary stimulated
⬇
Target gland releases hormone
⬇
Hormone level rises
⬇
Hypothalamus senses enough hormone
⬇
Stops releasing hormone
⬇
Hormone production decreases

Know this concept—it explains almost every endocrine pathway.

6. HPA Axis

Hypothalamus
⬇ CRH

Anterior Pituitary
⬇ ACTH

Adrenal Cortex
⬇ Cortisol

Cortisol

Major stress hormone

Functions:

• Increases blood glucose

• Helps body respond to stress

• Suppresses inflammation

• Suppresses immune response

Peak cortisol:
6–9 AM

Lowest:
Nighttime

⭐ Drugs to Know

Must Know DiseasesDiabetes Insipidus

• ADH deficiency

• Large amounts of dilute urine

• Dehydration

• Treated with Desmopressin (DDAVP)

Cushing Syndrome

Too much cortisol

Classic findings:

• Moon face

• Buffalo hump

• Truncal obesity

• Hypertension

• Osteoporosis

Addison Disease

Too little cortisol

Symptoms:

• Fatigue

• Weight loss

• Hypotension

• Hyponatremia

• Hyperkalemia

• Dehydration

Stress can cause Addisonian crisis (medical emergency).

Medication Pearls ⭐Prednisone

Remember:

• Give in the morning with breakfast

• Never stop suddenly

• Taper after long-term use

• Causes hyperglycemia

• Increases infection risk

• Long-term use → osteoporosis & Cushingoid features

Desmopressin

Watch for:

• Water intoxication

• Fluid overload

• Hyponatremia

Monitor:

• I&O

• Daily weights

• Electrolytes

Somatropin

Monitor:

• Long bone growth

• Growth plate closure

• Nutrition

• Injection site reactions

Fludrocortisone

Monitor:

• Blood pressure

• Sodium

• Potassium

• Edema

• Weight gain

1. Thyroid Gland BasicsLocation

• Located in the middle of the neck

• Surrounds the trachea like a shield

• Consists of two lobes

Hormones Produced

1. Thyroid Hormone

   • T3 (Triiodothyronine)

   • T4 (Thyroxine)

2. Calcitonin

   • Regulates calcium levels

   • Balances the effects of parathyroid hormone (PTH)

Iodine

• Required to produce T3 and T4.

• Must obtain iodine from the diet.

2. Hypothalamic-Pituitary-Thyroid (HPT) Axis ⭐⭐⭐⭐⭐

Know this pathway!

Hypothalamus
⬇ TRH (Thyrotropin-Releasing Hormone)

Anterior Pituitary
⬇ TSH (Thyroid Stimulating Hormone)

Thyroid Gland
⬇ T3 + T4

Body
⬇
Controls metabolism

Negative Feedback

When T3/T4 levels increase:

• Hypothalamus decreases TRH.

• Pituitary decreases TSH.

• Thyroid hormone production slows.

3. What Does Thyroid Hormone Do?

Think: METABOLISM

Thyroid hormones regulate:

• Basal metabolic rate

• Body temperature

• Heat production

• Oxygen consumption

• Cardiac output

• Blood volume

• Carbohydrate metabolism

• Fat metabolism

• Protein metabolism

• Growth & development

• Nervous system development

• Reproductive system function

4. HypothyroidismDefinition

Underactive thyroid gland

↓ T3
↓ T4

↓

Slow metabolism

Causes

• Thyroidectomy

• Iodine deficiency

• Hashimoto disease (autoimmune)

• Thyroid tumor

• Low TSH

• Low TRH

Signs & Symptoms

Everything is SLOW

• Cold intolerance

• Weight gain

• Fatigue

• Lethargy

• Constipation

• Dry skin

• Hair loss

• Bradycardia

• Thickened skin

• Slow metabolism

Memory Trick

HYPO = LOW & SLOW ❄🐢

5. HyperthyroidismDefinition

Overactive thyroid gland

↑ T3
↑ T4

↓

Fast metabolism

Common Cause

Graves Disease (autoimmune)

Signs & Symptoms

Everything is FAST

• Heat intolerance

• Tachycardia

• Weight loss

• Diarrhea

• Hypertension

• Tremors

• Restlessness

• Insomnia

• Enlarged thyroid (goiter)

Memory Trick

HYPER = HIGH & FAST 🔥⚡

6. Treatment GoalsHypothyroidism

Replace thyroid hormone.

Goal:
Euthyroid State (Normal thyroid function)

Medication:
Levothyroxine

Hyperthyroidism

Decrease thyroid hormone production.

Options:

• PTU

• Methimazole

• Radioactive iodine

• Thyroidectomy

Goal:
Eventually regulate with Levothyroxine if thyroid is destroyed or removed.

7. Levothyroxine (Synthroid) ⭐⭐⭐⭐⭐Drug Class

Thyroid hormone replacement

Used For

Hypothyroidism

Administration

• Oral

• Every morning

• Empty stomach

• Before breakfast

• Lifelong therapy

Onset

Slow

Peak effect:
1–3 weeks

How It Works

Increases:

• Metabolism

• Oxygen consumption

• Heart rate

• Growth

• Carbohydrate metabolism

• Fat metabolism

• Protein metabolism

Contraindications

Avoid or use cautiously in:

• Cardiovascular disease

• Thyrotoxicosis

Nursing Consideration

Hold medication if HR >100 bpm

A heart rate over 100 may indicate the dose is too high and the patient has become hyperthyroid.

Adverse Effects

Think:
Too much medication = Hyperthyroidism

• Tachycardia

• Hypertension

• Heat intolerance

• Diarrhea

• Weight loss

• GI upset

• Palpitations

Important

NOT used for weight loss.

Patient Teaching

• Take every morning.

• Empty stomach.

• Same time every day.

• Lifelong therapy.

• Annual thyroid lab tests.

• Report symptoms of hypo- or hyperthyroidism.

8. Graves DiseaseMost Common Cause

Hyperthyroidism

Characteristics

• Autoimmune disorder

• Enlarged thyroid (goiter)

• Excess thyroid hormone

Treatment:

• PTU

• Methimazole

• Radioactive iodine

• Thyroidectomy

9. PTU & MethimazoleDrug Class

Antithyroid medications

Purpose

Destroy or block thyroid hormone production.

Eventually:
Patient usually becomes hypothyroid and requires Levothyroxine replacement.

Adverse Effects

Think:
Destroy thyroid → Hypothyroidism

• Drowsiness

• Weight gain

• Fatigue

• Constipation

Specific adverse effects:

• PTU → Liver toxicity

• Methimazole → Bone marrow suppression

Contraindications

• Pregnancy

• Pediatric patients

Medication Summary

Hypothyroidism vs. Hyperthyroidism

1. Diabetes Mellitus BasicsDefinition

Diabetes Mellitus is a disorder characterized by:

• Hyperglycemia

• Relative or absolute lack of insulin

• Insulin resistance

• Impaired insulin receptors

Result:

• Altered metabolism of glucose, fats, and proteins.

Long-Term Complications

Chronic hyperglycemia damages blood vessels leading to:

• Retinopathy → vision loss

• Nephropathy → kidney disease

• Neuropathy → nerve damage

• Atherosclerosis

• Heart attack

• Stroke

Memory Trick

Diabetes = Blood vessel disease.

2. The Diabetic Zoo 🦁The Pancreas

Functions as:

• Endocrine gland

• Exocrine gland

Endocrine FunctionAlpha Cells 🐱

Release Glucagon

Triggered by:

• LOW blood sugar

Result:
↑ Blood glucose

Beta Cells 🐷

Release Insulin

Triggered by:

• HIGH blood sugar

Result:
↓ Blood glucose

Memory Trick

🐱 Cat = Glucagon = Glucose Goes Up

🐷 Pig = Insulin = Sugar Goes In

3. InsulinFunction

Moves glucose:

Bloodstream
⬇
Cells
⬇
Energy

Also:

• Stores glucose as glycogen

• Stores fat

• Promotes protein synthesis

Without insulin:

• Glucose stays in blood.

• Cells starve.

Biphasic Insulin Release

After eating:

Phase 1

• Rapid release (3–5 min)

Phase 2

• Longer release

• Covers the rest of the meal

Postprandial = After eating

4. Why Diabetes Happens

Three major causes:

1. Not enough insulin

2. Insulin resistance

3. Not enough insulin receptors

↓

Hyperglycemia

5. Glucagon

Released when blood sugar is LOW.

Functions:

• Breaks down liver glycogen

• Raises blood glucose

Think:

Glucagon = Emergency sugar supply.

6. HyperglycemiaSigns & Symptoms

The 3 Ps

• Polyuria

• Polydipsia

• Polyphagia

Also:

• Fatigue

• Glycosuria

• Weight loss

• Lipolysis

• Ketosis

• Protein breakdown

• Poor wound healing

Memory Trick

HIGH sugar = Hot & Dry.

DiagnosisFasting Blood Glucose

≥126 mg/dL

Hemoglobin A1C

≥6.5%

Measures:
Average blood sugar over 3 months

Goal:
<7%

Advantages:

• No fasting required

• Detects diabetes earlier than fasting glucose

7. Type 1 DiabetesCause

Autoimmune destruction of beta cells

↓

No insulin produced

Treatment

Lifelong insulin

Presentation

• Young onset

• Weight loss

• 3 Ps

• Ketoacidosis

Memory Trick

Type 1 = Need insulin to LIVE.

8. Type 2 DiabetesCause

Insulin resistance

AND/OR

Not enough insulin

Risk Factors

• Obesity

• Sedentary lifestyle

• Family history

Treatment

First-line:

• Diet

• Exercise

Then:

• Oral medications

• Insulin if needed

Type 1 vs Type 2

9. Hyperglycemia vs HypoglycemiaHyperglycemia

Think:

Hot & Dry

Signs:

• Polyuria

• Polydipsia

• Polyphagia

• Fruity breath

• Kussmaul respirations

• Dehydration

• Coma

Hypoglycemia

Blood glucose:
<60 mg/dL

Think:

Cold & Clammy — Need Some Candy

Signs:

• Tremors

• Sweating

• Headache

• Irritability

• Confusion

• Altered LOC

Treatment:

• If awake → juice, glucose tablets, regular soda

• If unconscious → IV dextrose or IM glucagon

10. Dawn vs Somogyi Phenomenon ⭐⭐⭐⭐⭐

11. Insulin TypesRapid Acting

Examples:

• Lispro

• Aspart

• Glulisine

Onset:
10–20 min

Peak:
1–3 hr

Duration:
2–5 hr

Meal coverage

Patient MUST eat.

Short Acting

Regular insulin

⭐ Only insulin given IV.

Intermediate Acting

NPH

Cloudy

Peak:
4–12 hr

Duration:
Up to 24 hr

Long Acting

• Glargine

• Detemir

No peak

Duration:
24 hr

Basal insulin

Never mix.

Basal vs Prandial InsulinBasal

Background insulin

Works all day

Examples:

• Glargine

• Detemir

Prandial

Meal insulin

Examples:

• Lispro

• Aspart

• Glulisine

• Regular

12. Insulin Nursing Considerations

• Rotate injection sites.

• Never inject cold insulin.

• Long-acting insulin is never mixed.

• NPH is cloudy.

• Monitor during peak for hypoglycemia.

• Exercise lowers insulin requirements.

• Stress increases insulin requirements.

13. Sulfonylureas

Examples:

• Glimepiride

• Glipizide

• Glyburide

Memory Trick

All begin with GLI-

Mechanism:
Stimulate beta cells to release insulin.

Main adverse effect:
Hypoglycemia

Contraindications:

• Type 1 diabetes

• Pregnancy

• Sulfa allergy

14. Metformin ⭐⭐⭐⭐⭐

Drug Class:
Biguanide

Mechanism:

• Decreases liver glucose production

• Increases insulin sensitivity

• Does NOT stimulate insulin release

Does NOT cause hypoglycemia.

Major Adverse Effect

Lactic Acidosis (Black Box Warning)

Nursing Pearls

Hold:

• Before IV contrast

• For 48 hours after IV contrast

• During major surgery until kidney function returns

Monitor:

• Kidney function (BUN/Creatinine)

15. GLP-1 Agonists

Mechanism:

• Increase insulin

• Decrease glucagon

• Slow gastric emptying

• Increase satiety

Adverse Effects:

• Hypoglycemia

• GI upset

• Pancreatitis

• Black Box Warning: Thyroid cancer

Contraindicated:
Family history of thyroid cancer.

1. Type 2 Diabetes ReviewWhat is Type 2 Diabetes?

Type 2 diabetes occurs when the body:

• Produces insulin but not enough OR

• Becomes resistant to insulin.

First-Line Treatment

• Diet

• Exercise

• Weight loss

If lifestyle changes aren't enough:

• Oral medications

• Injectable medications

• Insulin (if needed)

Remember: Type 2 diabetics usually have a functioning pancreas, so many medications work by improving insulin function rather than replacing it.

2. Sulfonylureas ⭐⭐⭐⭐⭐Drug Class

Stimulate insulin secretion from the pancreas.

Common Drugs

• Glimepiride

• Glipizide

• Glyburide

Memory Trick

GLI = "Lazy pancreas drugs"
They push the pancreas to release more insulin.

Mechanism of Action

• Stimulate pancreatic beta cells

• Increase insulin release

• Lower blood glucose

Used For

• Type 2 diabetes only

• Most effective early in the disease when beta cells still function

Contraindications

Do NOT use in:

• Type 1 diabetes

• Pregnancy

• Children

• Sulfa (sulfonamide) allergy

Adverse EffectsMost Important

Hypoglycemia

Also:

• Nausea

• Vomiting

• Anorexia

Nursing Considerations

• Monitor blood glucose.

• Teach patients to recognize hypoglycemia.

• Use cautiously if appetite is poor because skipping meals increases hypoglycemia risk.

3. Other Type 2 Diabetes Medications

These medications work in different ways to improve blood glucose control.

They may:

• Slow glucose absorption from the intestines.

• Increase insulin release.

• Improve insulin sensitivity.

• Reduce glucose production.

• Increase glucose excretion.

Goal:
Achieve good glycemic control while supporting diet and exercise.

4. Metformin (Biguanide) ⭐⭐⭐⭐⭐Drug Class

Biguanide

Mechanism of Action

Metformin:

• Decreases glucose production by the liver.

• Decreases intestinal glucose absorption.

• Increases insulin sensitivity.

Important: It does NOT stimulate insulin release, so it generally does not cause hypoglycemia when used alone.

Why is Metformin First-Line?

• Inexpensive

• Very effective

• Well tolerated

• Often combined with sulfonylureas

Major Adverse Effects

Common:

• GI upset

• Nausea

• Diarrhea

Black Box Warning ⭐⭐⭐⭐⭐

Lactic Acidosis

Rare but life-threatening.

Risk increases with:

• Kidney disease

• IV contrast dye

• Surgery

• Poor renal function

Nursing Considerations

Monitor:

• BUN

• Creatinine

• Kidney function

Hold Metformin:

• Before procedures using IV contrast

• On the day of the procedure

• For 48 hours after IV contrast

• Until kidney function returns to normal

5. GLP-1 Agonists ⭐⭐⭐⭐Mechanism of Action

GLP-1 agonists:

• Increase insulin release.

• Decrease glucagon secretion.

• Slow gastric emptying.

• Increase feelings of fullness (satiety).

Result:

• Lower blood glucose.

• Reduced appetite.

Used as an adjunct to:

• Diet

• Exercise

Given by subcutaneous injection.

Adverse Effects

Most common:

• Hypoglycemia

• GI upset

Serious:

• Pancreatitis

Black Box Warning

Risk of thyroid tumors seen in animal studies.

Contraindications

Avoid in patients with:

• Personal or family history of thyroid cancer

6. DPP-4 InhibitorsExample

• Sitagliptin

Mechanism of Action

These medications:

• Slow the breakdown of GLP-1.

• Prolong insulin release.

• Decrease glucagon secretion.

• Slow gastric emptying.

Think of them as helping the body's natural incretin hormones last longer.

Medication Summary

1. Incretin-Based Drugs

These medications are used to treat Type 2 Diabetes Mellitus.

They work by affecting the body's incretin hormones, which help regulate:

• Blood sugar

• Appetite

• Digestion

2. GLP-1 Agonists ⭐⭐⭐⭐⭐Common Drugs

All end in -tide

Examples:

• Dulaglutide (Trulicity)

• Exenatide (Byetta)

• Liraglutide (Victoza)

• Semaglutide (Ozempic)

• Tirzepatide (Mounjaro)

Memory Trick

GLP-1 = -TIDE drugs

Mechanism of Action

GLP-1 agonists mimic the natural GLP-1 hormone.

They:

• Increase insulin release from pancreatic beta cells

• Decrease glucagon secretion

• Slow gastric emptying

• Reduce appetite

• Increase satiety (feeling full)

Result:

• Lower blood glucose

• Weight loss

Important Physiology

GLP-1:

• Increases insulin synthesis and secretion

• Lowers glucagon secretion

• Decreases liver glucose production

• Slows gastric emptying

• Lowers fasting and post-meal glucose

Key Point

GLP-1 does NOT increase insulin secretion if blood glucose is below 90 mg/dL, helping reduce the risk of hypoglycemia.

Uses

Approved for:

• Type 2 diabetes (with diet and exercise)

• Obesity

Weight-loss brands:

• Semaglutide (Wegovy)

• Tirzepatide (Zepbound)

• Liraglutide (Saxenda)

Administration:

• Subcutaneous (SQ) injection

• Can be given without regard to meals

Adverse Effects

Common:

• Nausea

• Vomiting

• Diarrhea

• Loss of appetite

Serious:

• Hypoglycemia

• Pancreatitis

Black Box Warning ⭐⭐⭐⭐⭐

Thyroid cancer

Avoid in patients with a personal or family history of medullary thyroid carcinoma.

3. DPP-4 Inhibitors ⭐⭐⭐⭐Common Drugs

All end in -gliptin

Examples:

• Sitagliptin (Januvia)

• Saxagliptin (Onglyza)

• Alogliptin (Vipidia)

• Vildagliptin (Galvus)

Memory Trick

DPP-4 = -GLIPTIN drugs

Mechanism of Action

DPP-4 normally destroys GLP-1.

These medications block DPP-4, allowing GLP-1 to last longer.

Result:

• Increase insulin secretion

• Decrease glucagon release

• Lower liver glucose production

• Improve blood sugar control

Unlike GLP-1 agonists, they are weight neutral.

Uses

Used as an adjunct to:

• Diet

• Exercise

Advantages:

• Safe for older adults

• Safe in many patients with renal or hepatic impairment

• Low risk of hypoglycemia

Administration:

• Oral (PO)

• Once daily

Adverse Effects

Usually well tolerated.

Possible side effects:

• Headache

• GI upset

  • Nausea

  • Vomiting

  • Diarrhea

  • Constipation

Minimal risk of hypoglycemia.

GLP-1 vs. DPP-4 Comparison