Endocrine and metabolic medications: a nursing reference

Endocrine pharmacology is tested heavily on the NCLEX and encountered daily in med-surg, ICU, and outpatient settings. Nurses must manage insulin regimens, recognize hypoglycemia versus diabetic ketoacidosis, monitor thyroid replacement, and understand why corticosteroids can never be stopped abruptly. Mistakes in this drug class kill patients.

This reference covers five major categories: insulin therapy, oral antidiabetic agents, thyroid medications, corticosteroids, and adrenal agents. For each class you’ll find mechanism of action, key nursing considerations, critical safety parameters, and the NCLEX pearls examiners test most often. Use it alongside the diabetes mellitus nursing reference, the hypothyroidism nursing reference, the hyperthyroidism nursing reference, the Addison’s disease nursing reference, and the Cushing’s syndrome nursing reference.

Fast-scan: endocrine drug categories at a glance

Insulin therapy

Insulin is the cornerstone of type 1 diabetes management and a critical tool in type 2 diabetes when oral agents no longer provide adequate glycemic control. Understanding insulin types is mandatory knowledge for nursing practice — incorrect timing, dosing, or mixing of insulin types causes hypoglycemia, a preventable medical emergency.

Insulin types and pharmacokinetics

The table below summarizes onset, peak, and duration for every major insulin type. These numbers reflect subcutaneous administration; IV insulin (regular only) has different kinetics.

Nursing considerations for insulin

Glucose monitoring: Check blood glucose before every insulin dose. Know the facility’s hold parameters — most protocols hold insulin if the blood glucose is below 70 mg/dL and notify the provider. For sliding-scale coverage, confirm the patient has eaten or will eat before giving rapid-acting insulin.

Hypoglycemia recognition and treatment: Blood glucose below 70 mg/dL defines hypoglycemia. Signs and symptoms divide into two categories. Adrenergic (early): diaphoresis, tachycardia, tremors, anxiety, palpitations. Neuroglycopenic (late, more serious): confusion, slurred speech, seizures, loss of consciousness. Conscious patients who can swallow: 15 grams of fast-acting carbohydrates (4 oz juice, glucose tablets), recheck in 15 minutes (“15–15 rule”). Unconscious or NPO patients: 50% dextrose (D50W) IV push or glucagon IM/SubQ.

Differentiating hypoglycemia from DKA (NCLEX high-yield): These two states can be confused — both cause altered mental status — but treatment is opposite.

Injection sites: Abdomen (fastest absorption), outer thigh, upper outer arm, upper buttock. Rotate sites within the same anatomical region to prevent lipohypertrophy. Lipohypertrophied tissue absorbs insulin erratically — inspect injection sites at every visit.

Storage: Unopened insulin vials/pens are refrigerated (35–46°F). In-use vials and pens can be kept at room temperature for up to 28–30 days (check manufacturer labeling — varies by product). Protect from heat, sunlight, and freezing. Never use cloudy rapid-acting or long-acting insulin (cloudiness = degradation).

Sick-day rules: Insulin is never stopped during illness, even if the patient is not eating. Illness raises counterregulatory hormones (cortisol, glucagon, epinephrine), increasing blood glucose. Patients should check glucose every 2–4 hours when ill, stay hydrated, and contact their provider if glucose remains elevated or ketones are present in urine.

NCLEX pearl — “clear before cloudy” mixing rule: When mixing regular insulin with NPH, draw up the clear (regular) insulin first, then the cloudy (NPH) insulin. This prevents contaminating the regular insulin vial with NPH, which would alter the regular insulin’s pharmacokinetics. Memory aid: “Clear before cloudy, regular before NPH.” Long-acting insulins (glargine, detemir, degludec) are NEVER mixed with any other insulin.

Oral antidiabetic agents

Oral agents for type 2 diabetes work through diverse mechanisms — reducing hepatic glucose output, stimulating insulin secretion, mimicking incretin hormones, or promoting glucosuria. Each class carries a distinct nursing safety profile.

Metformin and IV contrast: the key clinical rule

Metformin is held before procedures using iodinated IV contrast because contrast nephropathy can impair renal clearance of metformin, leading to metformin accumulation and potentially fatal lactic acidosis. The standard protocol: hold metformin 48 hours before elective contrast procedures, check renal function 48 hours after, and restart only if eGFR remains adequate. This interaction is highly tested on NCLEX and appears frequently in clinical scenarios — see also the cardiovascular medications reference for additional contrast precautions.

SGLT-2 inhibitors and euglycemic DKA

One of the most dangerous, underrecognized adverse effects of SGLT-2 inhibitors is diabetic ketoacidosis with near-normal blood glucose — called euglycemic DKA. The mechanism: SGLT-2 inhibition shifts the body toward fat oxidation and ketone production, and low insulin states (fasting, surgery, illness) accelerate this. Blood glucose may be 130–200 mg/dL even while the patient develops metabolic acidosis with elevated ketones. Nurses must recognize this pattern: metabolic acidosis + elevated ketones + history of SGLT-2 inhibitor use, even with normal glucose, requires urgent evaluation. For patients using these agents, hold 3–4 days before elective surgery and monitor for dehydration.

Thyroid medications

Thyroid pharmacology covers two opposing clinical scenarios: replacement therapy for hypothyroidism and suppression or ablation therapy for hyperthyroidism. These drugs have narrow therapeutic windows and significant drug interactions. See the hypothyroidism nursing reference and hyperthyroidism nursing reference for full clinical management context.

Levothyroxine (Synthroid, Levoxyl, Tirosint)

Mechanism: Levothyroxine is synthetic T4. The body converts T4 to the active T3 form. It replaces endogenous thyroid hormone in hypothyroidism and suppresses TSH in thyroid cancer management.

Administration — timing is critical: Administer on an empty stomach 30–60 minutes before breakfast, or at bedtime at least 3–4 hours after the last meal. This maximizes absorption, which is significantly reduced by food, calcium, iron, and several medications.

Drug interactions that reduce levothyroxine absorption:

• Calcium carbonate — administer levothyroxine at least 4 hours apart from calcium supplements
• Iron supplements (ferrous sulfate) — separate by at least 4 hours
• Proton pump inhibitors (PPIs) — reduce gastric acid needed for dissolution; counsel patients taking both drugs
• Antacids (aluminum/magnesium hydroxide)
• Cholestyramine and colestipol (bile acid sequestrants) — separate by 4–6 hours

Consistent timing matters: Instruct patients to take levothyroxine at the same time every day. Even minor day-to-day variation in absorption (food, supplements) can destabilize thyroid levels. TSH is the primary monitoring parameter; it takes 4–6 weeks to reflect dose adjustments.

Signs of over-replacement (thyrotoxicosis): Tachycardia, palpitations, tremor, heat intolerance, weight loss, anxiety, insomnia, diarrhea. If a patient on levothyroxine develops these, the dose may be too high. In the elderly, cardiac effects dominate — atrial fibrillation is a common and dangerous consequence. The lab values cheat sheet includes TSH, free T4, and T3 reference ranges.

Antithyroid agents: methimazole and PTU

These drugs are used for Graves’ disease and in preparation for thyroidectomy or radioactive iodine therapy.

Mechanism: Both drugs inhibit thyroid peroxidase, the enzyme required to oxidize iodide and incorporate iodine into thyroid hormone synthesis. The result is reduced production of T3 and T4. They do not destroy existing hormone stores — effect takes weeks.

Propylthiouracil (PTU) has an additional mechanism: it also inhibits peripheral conversion of T4 to the more active T3, making it faster-acting in thyroid storm. PTU is also preferred in the first trimester of pregnancy because methimazole carries teratogenic risk (aplasia cutis, choanal atresia). After the first trimester, methimazole is preferred — PTU carries hepatotoxicity risk with prolonged use.

Critical nursing safety concern — agranulocytosis:

Both methimazole and PTU can cause agranulocytosis (severe neutropenia), a potentially fatal reduction in white blood cells that eliminates the body’s ability to fight infection. Onset is unpredictable and can occur months into therapy.

Nursing priority: Instruct every patient to stop the medication immediately and call their provider or go to the emergency department if they develop:

• Fever (even low-grade)
• Sore throat
• Mouth sores
• Signs of infection

This instruction must be reinforced at every encounter. A CBC with differential confirms agranulocytosis; the offending drug is permanently discontinued.

Lugol’s iodine (SSKI — saturated solution of potassium iodide):

Used pre-operatively before thyroidectomy and in thyroid storm management. High-dose iodine temporarily reduces thyroid vascularity and inhibits thyroid hormone release (Wolff-Chaikoff effect). It is not a long-term treatment — the gland eventually “escapes” this blockade. Administer through a straw (to protect dental enamel), diluted in juice. The taste is unpleasant — offer flavorings.

Radioactive iodine (I-131):

I-131 is concentrated in thyroid tissue and emits beta radiation that destroys thyroid cells. Used for Graves’ disease, toxic nodular goiter, and thyroid cancer ablation after thyroidectomy.

Radiation precautions (first 4–7 days after administration):

• Avoid close prolonged contact with pregnant women, infants, and children under 5
• Sleep alone; maintain 6-foot distance from others when possible
• Flush the toilet twice after use; wash hands thoroughly
• Use separate eating utensils; avoid sharing towels or linens
• Instruct patient that salivary gland tenderness may occur (radiation sialadenitis)

Most patients develop hypothyroidism after I-131 therapy and will require lifelong levothyroxine replacement.

Corticosteroids

Corticosteroids — both glucocorticoids and mineralocorticoids — are among the most widely used and most mismanaged drug classes in clinical practice. Their benefits are profound; their side effect burden is extensive. The single most dangerous nursing error with corticosteroids is abrupt discontinuation.

Glucocorticoids

Common drugs: Prednisone (oral), methylprednisolone (Solu-Medrol IV), dexamethasone (Decadron), hydrocortisone (Cortef, Solu-Cortef)

Mechanism: Glucocorticoids bind to intracellular glucocorticoid receptors and alter gene transcription, producing broad anti-inflammatory and immunosuppressant effects. They also affect glucose metabolism, bone density, fluid/electrolyte balance, mood, and immune function.

Clinical uses: Asthma exacerbations, COPD exacerbations, allergic reactions, autoimmune diseases (lupus, rheumatoid arthritis, IBD), organ transplant rejection prophylaxis, cerebral edema, septic shock (physiologic doses), adrenal insufficiency replacement, chemotherapy antiemesis (dexamethasone), palliative care (appetite, energy, pain).

Corticosteroid side effects by system

The mnemonic CUSHINGOID captures the major adverse effects of chronic glucocorticoid use:

C — Cataracts (posterior subcapsular) U — Ulcers (peptic ulcer disease, GI bleeding — administer with food or a PPI) S — Skin thinning, striae, easy bruising, impaired wound healing H — Hypertension (sodium and water retention) I — Infections (impaired immune function — live vaccines contraindicated) N — Necrosis of the femoral head (avascular necrosis — report hip/groin pain) G — Glucose elevation (steroid-induced hyperglycemia — monitor glucose in all patients) O — Osteoporosis (calcium and vitamin D supplementation recommended; bisphosphonates for long-term users) I — Insomnia, mood changes, psychosis (steroid-induced psychiatric effects — see the psychiatric medications reference for corticosteroid-induced mood disorder management) D — Diabetes/Depression (both new-onset and worsening of pre-existing conditions)

The abrupt discontinuation rule

Exogenous glucocorticoids suppress the hypothalamic-pituitary-adrenal (HPA) axis. The adrenal glands, receiving the signal that cortisol is adequate, reduce endogenous production. With prolonged use, the glands atrophy. Abrupt withdrawal removes both exogenous and endogenous cortisol simultaneously — the patient is left with no cortisol, which causes adrenal crisis: hypotension, fever, nausea, vomiting, weakness, severe abdominal pain, and potentially circulatory collapse and death.

Nursing action: Corticosteroids are always tapered, never stopped abruptly. The taper duration depends on how long the patient has been on steroids. Even patients on short courses (>7–10 days of daily prednisone) may need a taper. Educate patients explicitly: never skip doses, never stop on their own, carry an emergency steroid injection kit if on long-term therapy.

Mineralocorticoids: fludrocortisone

Drug: Fludrocortisone (Florinef)

Mechanism: Fludrocortisone is a synthetic mineralocorticoid that acts on renal collecting tubules to promote sodium reabsorption and potassium excretion — the same mechanism as endogenous aldosterone.

Primary use: Replacement therapy in Addison’s disease (primary adrenal insufficiency), where both cortisol and aldosterone are deficient. Also used in salt-wasting congenital adrenal hyperplasia and postural hypotension syndromes.

Nursing considerations:

• Monitor blood pressure (hypertension is a sign of over-replacement)
• Monitor potassium — hypokalemia indicates excess mineralocorticoid effect
• Monitor weight and edema — sodium and water retention cause peripheral edema
• Monitor patients for signs of under-replacement: orthostatic hypotension, dizziness, salt craving

Adrenal agents

Hydrocortisone and fludrocortisone in Addison’s disease

Patients with Addison’s disease (primary adrenal insufficiency) produce neither cortisol nor aldosterone. Replacement requires both:

• Hydrocortisone 15–25 mg/day in divided doses (two-thirds in the morning, one-third in the afternoon) to mimic the natural diurnal cortisol pattern
• Fludrocortisone 0.05–0.2 mg/day to replace aldosterone

Because the adrenal gland cannot respond to physiological stress, these patients are at high risk for adrenal crisis during illness, injury, or surgery. The Addison’s disease nursing reference covers clinical assessment in detail.

Stress dosing: the sick-day rule for adrenal insufficiency

Patients on chronic corticosteroid replacement must increase their dose during physiological stress. Endogenous cortisol production can increase 5–10 fold during severe illness or surgery; patients with adrenal insufficiency cannot mount this response without dose adjustment.

Standard sick-day protocol:

• Minor illness (fever, nausea, vomiting, minor injury): double or triple the daily hydrocortisone dose
• Major surgery or critical illness: IV hydrocortisone 50–100 mg every 6–8 hours, then taper back to baseline as the patient recovers
• If the patient cannot take oral medications (vomiting, unconscious): IM/IV hydrocortisone is mandatory — instruct patients to carry an emergency hydrocortisone injection kit (Solu-Cortef Act-O-Vial) and wear a medical alert bracelet

NCLEX priority: A patient with Addison’s disease presenting to the emergency department with severe hypotension, tachycardia, fever, and confusion during a febrile illness is in adrenal crisis. The nursing priority is: establish IV access, administer IV hydrocortisone (or dexamethasone) immediately, IV fluid resuscitation, and glucose monitoring. Do not delay treatment waiting for lab results.

Agents for Cushing’s syndrome

When Cushing’s syndrome results from excessive cortisol production (from an adrenal tumor or ectopic ACTH source), medical therapy may be used while surgical management is planned or after failed surgery. See the Cushing’s syndrome nursing reference for full management context.

Metyrapone: Blocks cortisol synthesis by inhibiting 11-beta-hydroxylase. Used as a diagnostic test and as short-term medical therapy. Monitor for hypotension, nausea, and adrenal insufficiency with over-treatment.

Mitotane (Lysodren): Cytotoxic agent that destroys adrenal cortical tissue. Used for adrenocortical carcinoma. Monitor for significant neurological side effects (dizziness, ataxia, confusion), adrenal insufficiency (replacement therapy is required), and elevated liver enzymes.

Mifepristone (Korlym): Blocks glucocorticoid receptors. Used when surgery is not an option. Because it blocks the receptor rather than reducing cortisol production, ACTH and cortisol levels rise during therapy — serum cortisol cannot be used to monitor treatment response; clinical signs are used instead.

NCLEX summary: endocrine pharmacology pearls

• “Clear before cloudy” — when mixing regular (clear) and NPH (cloudy) insulin, draw regular first to prevent contamination
• Metformin + IV contrast — hold metformin 48 hours before and 48 hours after; check renal function before restarting
• SGLT-2 inhibitors + surgery — hold 3–4 days before elective procedures; DKA risk even with normal blood glucose
• Levothyroxine — empty stomach, same time daily; separate from calcium, iron, and PPIs by 4+ hours
• Methimazole/PTU — fever + sore throat = stop immediately and report; agranulocytosis is the priority concern
• Corticosteroids — NEVER stop abruptly regardless of dose or duration; taper always required
• Stress dosing — any patient on chronic corticosteroids (including Addison’s disease replacement) needs dose escalation during illness, injury, or surgery
• Sulfonylureas — hypoglycemia risk even without excess insulin; especially dangerous in the elderly and fasting patients
• GLP-1 agonists + DPP-4 inhibitors — pancreatitis is the critical adverse effect to monitor; teach patients to report severe abdominal pain immediately
• Pioglitazone (TZD) — contraindicated in NYHA Class III–IV heart failure; fluid retention and edema are expected

For laboratory monitoring parameters associated with these medications — including blood glucose targets, TSH ranges, and electrolyte goals — see the nursing lab values cheat sheet.