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Thyroid

  • The thyroid and parathyroid glands are essential endocrine glands located in the neck, playing crucial roles in metabolism, growth, and calcium regulation.

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Thyroid Gland Hormones and Regulation

  • Hypothalamus: Secretes Thyrotropin-Releasing Hormone (TRH).

  • Pituitary Gland: Stimulated by TRH to secrete Thyroid-Stimulating Hormone (TSH).

  • Thyroid Gland: Stimulated by TSH to produce:

    • Triiodothyronine ( T_3 )

    • Thyroxine ( T_4 )

    • Calcitonin

  • Negative Feedback Inhibition: High levels of thyroid hormones T3 and T4 inhibit the release of TRH from the hypothalamus and TSH from the pituitary gland.

Functions of Thyroid Hormones (T3 and T4)

Thyroid hormones exert effects on nearly every organ and tissue in the body, controlling:

  • Metabolic rate

  • Cell replication

  • Brain development

  • Overall growth and development

  • Muscle and digestive function

  • Bone maintenance

  • Tissue function

  • Tissue thermogenesis (heat production)

  • Serum cholesterol levels

  • Vascular resistance

Controls MOST systems in the body

Thyroid Assessment and Labs

  • Physical Assessment: Palpation and auscultation of the thyroid gland.

  • Laboratory Tests:

    • TSH (Thyroid-Stimulating Hormone): Normal range 0.45 - 4.5 \; u/ml .

    • Free T4 (Thyroxine): Measures unbound T4 0.7 - 2 ng/dL (ionized form of the t4)

    • T3/T4 (Total Triiodothyronine and Thyroxine).

    • T_3 Resin Uptake: Indirect measure of unbound thyroid hormone.

    • Thyroid Antibodies: Indicate autoimmune conditions (e.g., Hashimoto's disease).

    • Serum Thyroglobulin: Looks for thyroid carcinoma.

  • Radioactive Iodine: Used in diagnostic scans and uptake tests.

Thyroid Diagnostics

  • Thyroid Ultrasound: Uses high-frequency sound waves to create images of the thyroid gland.

  • Biopsy: Tissue sample taken for pathological examination.

  • Thyroid Scan: Utilizes radioactive iodine to assess the structure and function of the gland.

Parathyroid Gland

  • Function: Secretes Parathyroid Hormone (PTH)

  • Role in Calcium Homeostasis: Maintains a constant concentration of calcium ( Ca^{++} ) in the blood by:

    • Promoting Resorption: Mobilization of calcium from bones into the bloodstream.

    • Increasing Renal Reabsorption: Enhances calcium reabsorption by the kidneys.

    • Increasing Intestinal Absorption: Increases intestinal absorption of calcium by activating Vitamin D

      Mechanisms of action of parathyroid hormone. | Download Scientific Diagram

Calcium ( Ca^{++} )

Normal Ranges:

  • Ionized: 4.5 - 5.5 \; mg/dL

  • Total: 8.6 - 10.2 \; mg/dL

Functions:

  • Formation and structure of bones and teeth

  • Nerve impulse transmission

  • Muscle contraction

  • Blood coagulation

Regulation of Calcium Levels:

  • Decrease in Ca^{++} :

    • Parathyroid Hormone (PTH) is secreted

    • Leads to the release of free calcium from bone (resorption)

    • Stimulates Vitamin D activation, which increases intestinal calcium absorption

  • Increase in Ca^{++} :

    • Thyrocalcitonin (TCT), also known as calcitonin, is secreted by the thyroid gland.

    • PTH secretion is inhibited.

    • Inhibition of bone resorption occurs.

    • Inhibition of Vitamin D activation.

    • Increases renal excretion of calcium.

  • Dietary Intake: Absorbed through dietary sources such as yogurt, milk, cheese, rhubarb, collard greens, green leafy vegetables, fish, and beans.

  • Storage: Primarily stored in the bones.

Hypocalcemia (Low Calcium Levels)

Causes:

  • Inadequate dietary intake

  • Increased calcium excretion.

  • Decrease in the ionized fraction of calcium.

  • Endocrine disturbances (e.g., hypoparathyroidism).

Assessment/Clinical Manifestations:

  • Overall: Depolarization occurs more easily and at inappropriate times, leading to increased neuromuscular excitability.

  • Neurological: Paresthesias (tingling/numbness), tetany (muscle spasms), seizures.

  • Specific Signs:

    • Positive Trousseau's Sign: Carpal spasm induced by inflating a blood pressure cuff above systolic pressure for several minutes.

    • Positive Chvostek's Sign: Facial twitching when the facial nerve is tapped.

  • Cardiac: Decreased myocardial contractility. The cells are individually contracting at different times.

  • Osteoporosis

Treatment:

  • Drug therapies.

  • Oral calcium supplements.

  • Intravenous (IV) calcium: Administered slowly due to risks of EKG changes and extravasation.

  • Increase calcium absorption: Aluminum hydroxide, Vitamin D (monitor for toxicity)

  • \downarrow Nerve/Skeletal Muscle Excitability: Medications to reduce hyperexcitability

  • Bed rest is recommended to help manage symptoms and allow the body to stabilize.

Nursing Interventions:

  • Seizure precautions

  • Prevention of injury

  • Dietary modifications (calcium-rich foods).

Hypercalcemia (High Calcium Levels)

Causes:

  • Excessive intake of calcium

  • Renal failure

  • Thiazide diuretics

  • Hyperparathyroidism

  • Cancers (e.g., bone metastasis)

Assessment/Clinical Manifestations

  • Overall:less sensitive to normal stimuli

  • Disorientation, lethargy, slurred speech.

  • Increased urinary output, thirst (due to polyuria).

  • Nausea, vomiting, constipation.

  • Bone pain.

Treatment:

  • Address the underlying cause

  • If cancer-related: Surgery, chemotherapy, radiation, corticosteroids, bisphosphonates

  • If hyperparathyroidism: Partial parathyroidectomy

  • Dilution Therapy: Intravenous (IV) normal saline ( 0.9\% \; NS ) to promote renal excretion.

  • Drug therapies: Hold IV and oral medications containing calcium and Vitamin D

  • Loop diuretics: Furosemide to increase calcium excretion

  • Calcium resorption inhibitors: Calcitonin, plicamycin, low-dose aspirin, nonsteroidal anti-inflammatory drugs

  • Intravenous phosphate (use cautiously)

  • Dialysis in severe cases

Nursing Interventions

  • Mobilization (helps calcium return to bones)

  • Safety measures

  • Dietary modifications

  • Increase fluids (with sodium if not contraindicated) to prevent dehydration and promote renal excretion

Phosphate ( PO_4 )

  • Normal Range: 2.7 - 4.5 \; mg/dL .

Functions:

  • Acid-base balance.

  • Energy storage (e.g., ATP).

  • Bone and teeth formation.

  • Muscle and red blood cell formation.

Regulation:

  • Has an inverse relationship with calcium ( Ca^{++} ).

  • \uparrow PTH secretion results in \downarrow phosphate.

  • \downarrow PTH level increases extracellular fluid (ECF) phosphate concentration.

  • Food Sources: Absorbed through dietary intake from dairy products, red meat, poultry, seafood, legumes, and nuts.

Hypophosphatemia (Low Phosphate Levels)

Causes:

  • Malnutrition, malabsorption, nausea/vomiting.

  • Hypercalcemia.

  • Chronic alcoholism/withdrawal.

  • Diuretics.

  • Hyperventilation.

  • Diabetic Ketoacidosis (DKA).

Assessment/Clinical Manifestations:

  • Overall: Decreased energy metabolism, altered levels of other electrolytes and body fluids.

  • Respiratory: Respiratory failure.

  • Neurological: Seizures, paresthesias, confusion, irritability, fatigue, coma.

Interventions:

  • Discontinue medications that contribute to the problem (e.g., antacids, osmotic diuretics, calcium supplements).

  • Oral replacement.

  • Intravenous (IV) administration: Only if level is less than 1 \; mg/dL .

  • Determine and treat the underlying cause.

Hyperphosphatemia (High Phosphate Levels)

Causes:

  • Renal failure.

  • Hypoparathyroidism.

  • Some cancer interventions.

  • Hypocalcemia (often a consequence due to the inverse relationship).

Assessment/Clinical Manifestations:

  • Overall: Problems arise due to concurrent hypocalcemia. Increased sensitivity of excitable membranes, which may depolarize spontaneously and inappropriately.

  • Neuromuscular: Tetany, muscle weakness.

  • Gastrointestinal: Anorexia, nausea.

  • Cardiac: Tachycardia.

  • Signs and symptoms are often similar to those of hypocalcemia.

Interventions:

  • Calcitriol: (a form of Vitamin D) Can bind to phosphate in the GI tract.

  • Diuretics: Loop diuretics to increase renal excretion.

  • Dialysis in severe cases.

  • Treat associated low calcium levels.

  • Determine and treat the underlying cause.

Hypothyroidism

  • Definition: A condition resulting from insufficient thyroid hormone production.

Classifications:

  • Primary Hypothyroidism: The thyroid gland itself is not producing enough hormones T3/T4

  • Secondary Hypothyroidism: The pituitary gland is not secreting enough TSH.

  • Tertiary Hypothyroidism: The hypothalamus is not secreting enough Thyrotropin-Releasing Hormone (TRH).

Causes of Primary Hypothyroidism:

  • Autoimmune Thyroiditis (Hashimoto's Disease): Most common cause, immune system attacks the thyroid.

  • From treatment of hyperthyroidism: Radioiodine therapy, antithyroid medications, or thyroidectomy.

  • Post-radiation for head and neck cancers.

  • Iodine deficiencies, excess, or iodine compounds.

  • Medications: Lithium, Amiodarone.

  • Atrophy of the thyroid gland due to aging.

  • Diseases that infiltrate the thyroid: Amyloidosis, scleroderma, lymphoma.

Clinical Manifestations

  • Beginning Onset: Fatigue, lethargy, weight gain, cold intolerance, dry skin, brittle nails, deepening of the voice, subnormal temperature, bradycardia, slowed speech, enlarged tongue, constipation, apathy, flat affect.

  • Long-Term (without treatment): Dementia, sleep apnea, elevated cholesterol, atherosclerosis, coronary artery disease, diabetes.

Pharmacology

  • Levothyroxine (Synthroid, Levothroid, Levoxyl): Synthetic T4 which then turns into T3 in the body, allowing for normal action.

    • Reactions: Can cause symptoms of hyperthyroidism, arrhythmias, hypertension.

    • Teaching: Take at the same time each day, on an empty stomach ( 0.5 - 1 \; hour before breakfast). Administered and titrated based on thyroid panel results. Long-term use requires monitoring for osteoporosis. Many medication/food interactions (e.g., antacids, anticoagulants).

  • Liothyronine (Cytomel, L-triiodothyronine): Synthetic T_3 .

Nursing Management (Hypothyroidism):

  • Promote safe activity.

  • Monitor body temperature (due to cold intolerance).

  • Monitor for constipation.

  • Medication management (adherence, side effects, interactions).

  • Educate on signs and symptoms of medical emergencies.

Myxedema Coma:

  • Definition: A rare, severe, life-threatening form of hypothyroidism.

  • Causes: Undiagnosed hypothyroidism, infection, illness, exposure to cold, certain medications (opioids, sedatives, anesthesia).

  • Symptoms: Decreased temperature ( \downarrow \text{Temp} ), decreased respirations ( \downarrow \text{Resp} ), decreased blood pressure ( \downarrow \text{BP} ), decreased blood glucose ( \downarrow \text{Blood Glucose} ), decreased sodium ( \downarrow \text{Na}^+ ), unresponsiveness.

  • Warm slow, and inside out. to decrease chance of blood moving to perphrials

  • Treatment: Thyroid hormone replacement (IV), fluids, glucose administration, oxygen supplementation, assisted ventilation, warming blankets (avoid heating pads to prevent increased oxygen demand), avoid hypotension.

Home Care:

  • Medication management

  • Education on when to seek medical care

  • Dietary considerations

  • Importance of follow-up appointments

Hyperthyroidism (Thyrotoxicosis)

  • Definition: Excessive thyroid hormone production and release.

Causes:

  • Graves' Disease: Autoimmune condition, most common cause.

    • Characterized by bulging eyes (exophthalmos) and goiter (enlarged thyroid).

  • Thyroiditis: Inflammation of the thyroid gland.

  • Toxic adenomas (benign thyroid tumors that autonomously produce hormones).

  • Goiters (enlarged thyroids) that become hyperactive

  • Over-medication with thyroid hormones

Assessment and Diagnostic Findings:

  • Physical Assessment: Enlarged thyroid gland, may have a thrill (palpable vibration) and bruit (audible vascular sound) over the thyroid.

  • Laboratory Assessment:

    • Free T_4 : Increased.

    • TSH: Decreased (due to negative feedback).

  • Radioactive Iodine Uptake: Increased (indicating hyperactive thyroid tissue).

Clinical Manifestations:

  • Neurological: Nervousness, hyper-irritability, fine tremors of the hands.

  • Cardiac: Palpitations, tachycardia, sometimes atrial fibrillation; can lead to heart failure/myocardial hypertrophy.

  • Thermoregulation: Always feeling hot, flushed skin, excessive sweating (diaphoresis).

  • Musculoskeletal: Muscle fatigue, weakness, thin skin.

  • Ocular: Protrusion of the eyeballs (exophthalmos) in Graves' disease.

  • Gastrointestinal/Weight: Increased appetite, but with weight loss.

Treatment Goals:

  • Reduce thyroid hyperactivity.

  • Relieve symptoms.

  • Prevent complications.

  • Treatment Modalities:

    • Pharmacologic therapy.

    • Radioactive iodine therapy.

    • Surgical management (thyroidectomy).

Medications:

  • Propylthiouracil (PTU): Blocks synthesis of thyroid hormones and conversion of T4 to T3 .

    • Nursing Considerations: Monitor cardiac symptoms, signs of hypothyroidism. Must be given orally. Watch for rash, nausea, vomiting, agranulocytosis (severe reduction in white blood cells), Lupus-like syndrome (SLE).

  • Methimazole (Tapazole): Inhibits synthesis of thyroid hormone.

    • Nursing Considerations: Similar to PTU, but generally considered more toxic and potent.

  • Sodium Iodide & Potassium Iodide (SSKI - Saturated Solution of Potassium Iodide): Suppresses release of thyroid hormone, often used as part of surgical preparation.

    • Nursing Considerations: Give 1 \; hour post PTU/Methimazole. Watch for edema, hemorrhage, GI upset. SSKI should be mixed with juice/milk and given with a straw (can stain teeth). Discontinue for rash with potassium iodide. Watch for signs of toxic iodism.

  • Beta Blockers (e.g., Propranolol): Beta-adrenergic blocking agents, used to relieve sympathetic symptoms (tachycardia, tremors, nervousness).

  • Nursing Considerations: Hold for bradycardia or decreased cardiac output. Use with caution in patients with heart failure.

Radioactive Iodine Therapy (I-131):

Most common treatment for graves

  • Action: Destroys thyroid cells.

  • Efficacy: A single dose is about 95\% effective.

  • Contraindications: Pregnancy, breastfeeding.

  • Side Effects: Hypothyroidism (common long-term side effect, starts after 2 years).

  • Stay isolated from pregnant people and babies.

Pre-Surgical Management (Thyroidectomy):

  • Performed only in special circumstances (e.g., large goiter, cancer, non-response to other treatments).

  • Removes most of the thyroid gland.

  • Pretreatment with medications (e.g., antithyroid drugs, iodine) to achieve euthyroid state and reduce gland vascularity.

  • Patient education regarding the procedure and post-operative care. (decrease stress)

Post-Surgical Management (Thyroidectomy):

  • Airway: Monitor respirations, stridor (harsh sound indicating airway obstruction), swelling, drooling, difficulty swallowing.

  • Circulation: Monitor for bleeding at the incision site.

  • Pain: Administer analgesia, support head and neck, semi-Fowler's position, relaxation techniques, ice collar.

  • Communication: Assess for hoarseness, sore throat, or voice changes due to laryngeal nerve irritation.

Complications:

  • Thyroid Storm: A severe, life-threatening exacerbation of hyperthyroidism immediately post-surgery.

  • Hypocalcemia: Can result from accidental removal or damage to the parathyroid glands during surgery.

  • Nutrition: Cool liquids and soft foods post-operatively.

Nursing Management (Hyperthyroidism):

  • Body Temperature: Provide a cool room, cool baths, cool/cold oral fluids, frequent bedding changes (due to heat intolerance).

  • Nutrition: Small/frequent meals, high calorie/high protein diet, replace fluids, daily weight monitoring, accurate intake and output.

  • Coping Measures and Improving Self-Esteem: Reassurance that emotional changes are part of the disorder and will improve with effective treatment. Provide a calm, quiet environment.

Thyroid Storm or Crisis

  • Definition: An extreme, life-threatening form of hyperthyroidism.

  • Early Assessment & Treatment: Crucial for survival.

Signs & Symptoms:

  • High fever (hyperthermia).

  • Tachycardia

  • Worsening symptoms related to hyperthyroidism (e.g., profuse diaphoresis, severe nervousness).

  • Altered mental state (delirium, psychosis, somnolence, unresponsiveness).

  • Abrupt onset

  • Untreated always fatal

Management:

  • Manage fever and heart rate ( \text{HR} ).

  • Administer oxygen ( \text{O}_2 ).

  • IV fluids with dextrose.

  • Bring thyroid levels down with antithyroid medications, iodine, and steroids.

Hypocalcemia Post-Thyroidectomy

  • Cause: Can result from accidental removal or damage to the parathyroid glands during thyroidectomy.

  • Signs & Symptoms: Reflect hypocalcemia, including muscle cramps, tetany, carpopedal spasms, and seizures.

  • Treatment: Focuses on correction of hypocalcemia, primarily with calcium replacement (oral or IV).

Discharge Teaching (Thyroid Conditions)

  • Medication management (dosage, timing, side effects, interactions).

  • Post-operative care (if applicable).

  • Monitoring for signs and symptoms of hyperthyroidism or hypothyroidism.

  • Importance of follow-up care and regular monitoring of thyroid function tests.