Glucocorticoids insulin short notes easy language
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π Short Notes: Glucocorticoids & Insulin
PART 1 - GLUCOCORTICOIDS
What are they?
Glucocorticoids are steroid hormones produced by the adrenal cortex (zona fasciculata). The main natural glucocorticoid is cortisol. Synthetic versions include prednisone, dexamethasone, methylprednisolone, betamethasone, triamcinolone.
Mechanism of Action (How they work)
Think of it in two steps:
- Cortisol enters the cell and binds to the Glucocorticoid Receptor (GR) in the cytoplasm.
- The cortisol-GR complex does two things:
- Transactivation - Goes into the nucleus, binds to glucocorticoid response elements (GREs), and turns on anti-inflammatory genes.
- Transrepression - Forms dimers with NF-kB and AP-1 (pro-inflammatory transcription factors) and switches them OFF - this is the main anti-inflammatory mechanism.
In simple words: Glucocorticoids enter the cell, find the "on switch" for inflammation, and turn it off.
Key enzyme: 11Ξ²-HSD1 converts inactive cortisone β active cortisol in tissues. 11Ξ²-HSD2 in the kidney converts cortisol β cortisone to protect mineralocorticoid receptors.
(Harrison's Principles of Internal Medicine 22E)
Pharmacological Effects
| System | Effect |
|---|---|
| Metabolism | β Gluconeogenesis, β blood sugar, β fat breakdown (lipolysis), β protein catabolism |
| Anti-inflammatory | β Prostaglandins (inhibit COX-2), β leukotrienes, β cytokines, β histamine |
| Immune | Suppress T-cell activation, β antibody production |
| Cardiovascular | β Blood pressure (mineralocorticoid-like effect) |
| Bone | β Calcium absorption, β osteoblast activity β osteoporosis |
| Skin | Thinning, striae |
| CNS | Euphoria (short term), depression/psychosis (long term) |
Clinical Uses
- Inflammatory diseases - Rheumatoid arthritis, asthma, IBD, SLE
- Allergic reactions - Anaphylaxis (adjunct), urticaria
- Shock - Septic shock (hydrocortisone)
- Brain edema - Dexamethasone
- Immunosuppression - Organ transplant, autoimmune conditions
- Adrenal insufficiency (replacement therapy)
- Fetal lung maturity - Betamethasone given to mothers before premature delivery
Common Synthetic Glucocorticoids (Duration of Action)
| Drug | Type | Key Feature |
|---|---|---|
| Hydrocortisone | Short-acting | Has mineralocorticoid activity too |
| Prednisone/Prednisolone | Intermediate | Most common oral steroid |
| Methylprednisolone | Intermediate | IV use (pulse therapy) |
| Dexamethasone | Long-acting | No mineralocorticoid effect; used for brain edema, fetal lung maturity |
| Betamethasone | Long-acting | Crosses placenta well |
(Lippincott Illustrated Reviews Pharmacology; Rheumatology - Elsevier)
Adverse Effects (Side Effects) - "CUSHINGOID"
These develop with long-term use:
- C - Centripetal obesity (fat redistribution - moon face, buffalo hump)
- U - Ulcers (peptic ulcer - increased gastric acid)
- S - Skin changes (striae, thinning, easy bruising)
- H - Hyperglycemia (steroid-induced diabetes)
- I - Infection susceptibility β (immunosuppression)
- N - kNee/bone pain - Osteoporosis, avascular necrosis
- G - Growth retardation (children)
- O - Ophthalmic - Cataracts, glaucoma
- I - Impaired wound healing
- D - Dyslipidemia, hypertension
Important: Abrupt withdrawal after long-term use β Adrenal crisis (the adrenal gland stops producing cortisol). Always taper the dose slowly!
PART 2 - INSULIN
What is it?
Insulin is a polypeptide hormone made of two chains (A and B) connected by disulfide bonds. It is secreted by Ξ²-cells of the islets of Langerhans in the pancreas. It is made from proinsulin, which is cleaved into insulin + C-peptide.
Note: C-peptide is measured to check endogenous insulin production (exogenous insulin has no C-peptide).
How Insulin Secretion is Triggered (Mechanism)
- Blood glucose rises β glucose enters Ξ²-cell via GLUT-2 transporter
- Glucose is phosphorylated by glucokinase (glucose sensor)
- ATP is produced β K+ channels close β membrane depolarizes
- Voltage-gated Ca2+ channels open β Ca2+ enters
- Ca2+ triggers insulin exocytosis (release)
Sulfonylureas act here (they block K+ channels directly β force insulin release)
(Lippincott Illustrated Reviews Pharmacology)
Actions of Insulin (What insulin does)
| Target Organ | Effect |
|---|---|
| Liver | β Glycogen synthesis, β gluconeogenesis, β glycogenolysis, β lipogenesis |
| Muscle | β Glucose uptake (via GLUT-4), β glycogen & protein synthesis |
| Fat (Adipose) | β Glucose uptake, β lipogenesis, β lipolysis |
| Overall | β Blood glucose, β free fatty acids, β ketone bodies |
In simple words: Insulin is the "store energy" hormone. When glucose is high, insulin tells cells to take it up, store it as glycogen or fat, and stop breaking down stores.
Insulin Preparations - Types
All insulins are given subcutaneously (SC). Regular insulin can be given IV in emergencies (e.g., DKA).
| Type | Examples | Onset | Duration | When to Give |
|---|---|---|---|---|
| Rapid-acting | Lispro, Aspart, Glulisine | 15 min | 3-5 hrs | Just before meals |
| Short-acting (Regular) | Regular/Soluble insulin | 30-60 min | 6-8 hrs | 30 min before meals; also used IV |
| Intermediate-acting | NPH (Isophane) | 1-2 hrs | 12-18 hrs | Twice daily |
| Long-acting | Glargine, Detemir | 1-2 hrs | 20-24 hrs | Once daily (basal) |
| Ultra long-acting | Degludec | 1-2 hrs | >42 hrs | Once daily |
| Premixed | 70/30 (NPH/Regular) | - | - | Twice daily |
Memory trick for rapid-acting insulins: LAG = Lispro, Aspart, Glulisine
(Lippincott Illustrated Reviews Pharmacology)
Insulin Regimens
- Standard therapy: 2 injections/day (usually premixed)
- Intensive therapy (Basal-Bolus): Long-acting insulin once daily (basal) + rapid-acting before each meal (bolus). Target A1C β€ 7%. Better for preventing microvascular complications (retinopathy, nephropathy, neuropathy) but higher risk of hypoglycemia.
Adverse Effects
| Side Effect | Details |
|---|---|
| Hypoglycemia | Most common and dangerous. Sweating, tremor, confusion, palpitations. Treat with oral glucose or IV dextrose. |
| Weight gain | Insulin promotes fat/glycogen storage |
| Lipodystrophy | Fat atrophy or hypertrophy at injection sites (rotate sites!) |
| Hypokalemia | Insulin drives K+ into cells (used to treat hyperkalemia) |
| Insulin allergy | Rare with human recombinant insulin |
When to Use Insulin
- Type 1 Diabetes - Always needed (no endogenous insulin)
- Type 2 Diabetes - When oral drugs fail or during illness/surgery
- Gestational diabetes - Preferred over oral agents
- DKA/HHS - IV regular insulin
- Hyperkalemia - Insulin + dextrose (drives K+ into cells)
Key Differences: Glucocorticoids vs Insulin
| Feature | Glucocorticoids | Insulin |
|---|---|---|
| Type | Steroid hormone | Polypeptide hormone |
| Source | Adrenal cortex | Pancreatic Ξ²-cells |
| Effect on blood glucose | β (raises it) | β (lowers it) |
| Receptor | Intracellular (nuclear) | Cell surface (tyrosine kinase) |
| Route | Oral, IV, inhaled, topical | SC, IV |
| Long-term danger | Cushing's features | Hypoglycemia, weight gain |
Sources: Harrison's Principles of Internal Medicine 22E; Lippincott Illustrated Reviews Pharmacology; Rheumatology - Elsevier 2022
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