Endocrine Disorders-Montgomery

Endocrine Disorders

  • Presented by: Susan Montgomery, DNP, FNP-BC

Thyroid Feedback Loop

  • Homeostasis

    • Disrupted State:

      • Decreased T3 and T4 concentrations in blood or low body temperature.

    • Hypothalamus Activity:

      • Releases Thyrotropin-releasing hormone (TRH) to stimulate anterior pituitary.

    • Anterior Pituitary Response:

      • Releases Thyroid-stimulating hormone (TSH) in response to TRH.

    • Thyroid Gland Activation:

      • Thyroid follicles release T3 and T4, restoring normal levels and body temperature.

Tests of Thyroid Function

  • TSH (Thyroid-stimulating hormone):

    • Ultrasensitive assay for screening hyper/hypothyroidism.

    • Normal Range: 0.4-4.0 mIU/L.

    • Elevated levels (>4.0 mIU/L) indicate subclinical hypothyroidism; often asymptomatic but need monitoring.

  • Free T4:

    • Measures unbound thyroxine, metabolically active form.

    • Increased in hyperthyroidism; decreased in hypothyroidism.

  • T3:

    • Metabolically active form, elevated in hyperthyroidism.

    • Useful for diagnosing hyperthyroidism when T4 levels are normal. Not for hypothyroidism diagnosis.

  • Antibody Titers:

    • Antithyroglobulin and Antithyroperoxidase antibodies elevated in Graves' disease.

    • TSH receptor antibodies typically positive in Graves' disease.

Hypothyroidism

  • Prevalence:

    • Affects 1% of general population, 5% over age 60.

    • More common in females (5-8x) especially those over 40.

  • Causes:

    • Failure/destruction of thyroid gland.

    • Most common cause in U.S.: Hashimoto’s thyroiditis (autoimmune).

    • Other causes: severe non-thyroid illness (Euthyroid Sick Syndrome).

  • Clinical Manifestations:

    • Symptoms: mild to severe including weight gain, depression, cold intolerance, and more.

    • Physical findings: bradycardia, edema, skin pallor, goiter may be present.

Clinical Manifestations Cont.

  • Subclinical Hypothyroidism:

    • Normal serum free T4 with elevated TSH levels.

    • Often transient; monitoring required.

    • May benefit from levothyroxine replacement.

Labs for Hypothyroidism

  • Best screening test: Elevated TSH in primary hypothyroidism.

  • Free T4 may be low/normal.

  • Antibodies positive in autoimmune conditions.

  • Monitor CBC for anemia; lipid panel for hyperlipidemia.

Treatment of Hypothyroidism

  • Assess for adrenal insufficiency and cardiac issues before hormonal replacement.

  • First-line Medication: Levothyroxine (Synthroid).

    • Initial Dose: 25-50 mcg/day; usual therapeutic dose: 75-125 mcg/day.

    • Adjust dosage every 1-3 weeks based on TSH monitoring.

    • Elderly patients may require lower doses; pregnant women may need higher dosages.

  • Monitoring:

    • Recheck TSH 4-6 weeks after dose changes.

    • Medication adherence confirmation before dosage adjustment.

    • Caution with patients who have coronary artery disease.

Hyperthyroidism (Thyrotoxicosis)

  • Incidence: 1.3%, higher in women; common causes include Graves' disease, toxic multinodular goiter, and excess thyroid hormone.

Graves' Disease

  • Common in women aged 20-40, with genetic and environmental components.

  • Triggered by factors such as excessive iodine intake and other autoimmune conditions.

Toxic Multinodular Goiter

  • Common in elderly women; may involve toxic adenomas (Plummer disease).

Clinical Manifestations of Hyperthyroidism

  • Symptoms: weight loss, heat intolerance, nervousness, palpitations, etc.

  • Physical findings: exophthalmos, atrial fibrillation, tremors.

Labs in Hyperthyroidism

  • Decreased TSH, increased T4 and T3.

  • Detectable TSH receptor antibodies in many cases of Graves' disease.

Treatment of Hyperthyroidism

  • Propranolol: symptomatic relief; titrate dose as needed.

  • Methimazole: preferred treatment; taper before radioactive iodine therapy.

  • PTU: preferred during pregnancy; monitor closely.

Radioactive Iodine Treatment

  • Destroys overactive thyroid tissue; risk of future hypothyroidism.

  • Close monitoring required for thyroid hormone replacement needs post-treatment.

Surgery for Hyperthyroidism

  • Indicated for multinodular goiter or malignancy suspicion; also no control with medications during pregnancy.

Cushing’s Syndrome: Hypercortisolism

  • Caused primarily by excessive corticosteroid use or ACTH hypersecretion from tumors.

Signs & Symptoms of Cushing’s Syndrome

  • Central obesity, hypertension, muscle weakness, mood changes, etc.

Lab Findings for Cushing’s Syndrome

  • Elevated blood glucose and cortisol; low serum ACTH may indicate adrenal tumors.

    • Diagnostic Tests: Dexamethasone suppression test.

Treatment of Cushing's Syndrome

  • Surgical removal of tumors; tapering corticosteroid use when possible; patient education on stress management and infection avoidance.

Addison’s Disease

  • Chronic adrenal insufficiency, often autoimmune in origin.

Signs & Symptoms of Addison's Disease

  • Weakness, pigmentation changes, anorexia, hypotension.

Lab Findings in Addison's Disease

  • Low sodium, elevated potassium, low cortisol levels that fail to rise after ACTH administration.

Treatment of Addison’s Disease

  • Replacement therapy with hydrocortisone or prednisone; careful management in times of stress.