Thyroid Hormones and Related Disorders

Thyroid Gland Disorders

• Learning Objectives: Anatomy and physiology of the thyroid gland, thyroid disorders, causes of disorders, multisystem effects, diagnostics, and management of disorders are covered.

Anatomy and Physiology of the Thyroid Gland

• The thyroid gland is composed of two lobes connected by an isthmus.
• It's located in the front and on the sides of the trachea, below the larynx.
• The gland produces three hormones: T4 (thyroxine), T3(triiodothyronine), and calcitonin.
• T4 and T3 are produced in the thyroid follicles, requiring iodine (T4 has four iodine atoms, T3 has three). They have identical functions.
• Calcitonin is produced by parafollicular cells.

Thyroid Gland Hormones and Their Functions

• T3 and T4: Increase energy production and protein synthesis; enhance metabolic rate, regulating energy, and heat production; essential regulators of metabolic rate, playing critical roles in multiple body systems like the heart, brain, muscles, and others; essential for growth, development, and reproduction.
• Calcitonin: Regulates calcium and phosphate levels during childhood bone growth; maintains normal blood calcium and phosphate levels, crucial for strong bones.

Parathyroid Glands

• Usually, four parathyroid glands are present, two on the back of each thyroid lobe.
• Parathyroid hormone (PTH) has an antagonistic effect on calcitonin; its secretion is stimulated by low blood calcium levels (hypocalcemia) and inhibited by high blood calcium levels (hypercalcemia).
• Functions of PTH: maintains healthy blood calcium levels and stimulates calcium/phosphate release from bones, increasing their blood levels.

Thyroid Disorders

• Goiter: An enlarged thyroid gland. Often due to iodine deficiency. Cells may become overactive (hyperthyroidism), or underactive (hypothyroidism).

• Thyroiditis: Inflammation of the thyroid gland, a frequent cause of goiter. It can be subacute (viral), acute (bacterial), or chronic (autoimmune). Symptoms may include localized or diffused pain, radiating to throat, ears or jaw; fever, chills, sweats and fatigue. Risk factors include female sex, family history, older age and white ethnicity.

• Primary Hypothyroidism: Thyroid gland dysfunction.

• Secondary Hypothyroidism: Impaired TSH secretion, originating from the pituitary gland.

• Tertiary Hypothyroidism: Hypothalamus failure to release Thyroid-Releasing Hormone (TRH), resulting in decreased TSH release leading to diminished thyroid hormone secretion.

• Causes of Hypothyroidism: Thyroidectomy, radiation treatment, Hashimoto's disease (chronic autoimmune), inflammatory diseases; hypothalamic failure, inborn thyroid errors, insufficient hormone replacement therapy for hyperthyroidism, pituitary dysfunction, iodine deficiency, drugs (lithium, amiodarone, etc.).

• Causes of Hyperthyroidism: Family history, high iodine ingestion, trauma, toxic multinodular goiter, Graves' disease (genetic).

Multisystem Effects of Hypothyroidism

• Neurological: Hand and foot paresthesia (numbness/tingling), lethargy, somnolence, confusion, slow speech, memory impairment.
• Endocrine: Goiter.
• Respiratory: Pleural effusion.
• Gastrointestinal: Constipation.
• Musculoskeletal: Muscle stiffness, weakness, fatigue.
• Sensory: Periorbital edema (puffiness around the eyes).
• Cardiovascular: Hypotension, bradycardia, dysrhythmias, enlarged heart, anemia.
• Reproductive: Menorrhagia (female), infertility and decreased libido in females and males.
• Integumentary: Hair loss, brittle nails, dry skin and non-pitting edema.
• Metabolic: Hypothermia, anorexia, constipation, unexplained weight gain.
• Myxedema: The face of a person with Myxedema appears puffy; the voice is hoarse and husky; progressive, myxedema coma includes stupor, hypoventilation, hypoglycemia.

Multisystem Effects of Hyperthyroidism

• Neurological: Hand and eye tremors, nervousness, insomnia.
• Sensory: Blurred vision, photophobia.
• Cardiovascular: Hypertension, tachycardia, dysrhythmias, palpitations.
• Reproductive: Amenorrhea, decreased fertility (female), impotence, decreased libido (male).
• Integumentary: Fine, thin hair, flushed and moist skin.
• Endocrine: Goiter.
• Respiratory: Dyspnea.
• Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain.
• Musculoskeletal: Muscle wasting.
• Metabolic: Hyperthermia, diaphoresis (excessive sweating), hunger, weight loss, fluid volume deficit.

Thyroid Diagnostics

• Serum TSH, T3, T4 and free T4 levels are measured.
• T3 resin uptake test and radioisotope thyroid uptake tests are performed.
• Lab studies may show decreased serum T4, decreased blood glucose, decreased plasma osmolality, decreased TSH in pituitary/hypothalamic defects, increased TSH in thyroid defects, hyponatremia, hyperlipidemia, and lactic acidosis.

Thyroid Treatment

• Hypothyroidism: Lifelong hormone replacement with synthetic levothyroxine sodium or liothyronine sodium (Liotrix). Symptoms are usually relieved within 2–3 days of starting treatment. Myxedema coma requires immediate I.V. corticosteroids, glucose, and levothyroxine sodium.
• Hyperthyroidism: Antithyroid medications (methimazole, propylthiouracil) are usually used first; they block the production of thyroid hormones and usually provide improvement within two to four weeks. Beta-blockers may be used to control the effects of the sympathetic nervous system. Surgery (subtotal thyroidectomy) might be necessary in cases of a very large gland, or cases where the patient can't undergo other treatment, or if the patient has thyroid cancer. Radioactive iodine may also be an option depending on patient symptoms.

Nursing Responsibilities

• Hypothyroidism/Hyperthyroidism: Assessing for complications, monitoring and managing patient symptoms, vital signs, educating patients and families on the importance and use of medication.

• Thyroidectomy: Preoperative care, and postoperative care; management of hypothyroidism; providing health promotion about preventing hypothyroidism; and adequate iodine intake. Monitoring for increasing symptoms (including decreased level of consciousness, decreased vital signs, difficulties awakening or arousing). Respiratory support if needed, and close monitoring for other complications such as cardiac insufficiency. Avoiding unnecessary use of sedatives/analgesics.

• Radioactive Iodine Therapy: Assess for allergies, dilute iodine sources appropriately, monitor for increased bleeding risk if anticoagulants are also administered.

• Thyroid Storm/Crisis: Immediate treatment with antipyretics; maintain patent airway through suction and ventilatory support; careful administration of medications and fluids; monitoring of vital signs; environmental cooling (if necessary).

Nursing Diagnoses and Interventions (Specific examples)

• Activity intolerance: Promoting independence in self-care; provide rest and exercise as tolerated; assist with self-care activities; encourage conversation and non-stressful activities; monitor patient response to increasing activities.

• Risk for imbalanced body temperature: Provide extra layers of clothing or blankets, discourage use of heating pads/electric blankets; monitor body temperature and report decreases; protect from drafts.

• Constipation: Encourage increased fluid intake within fluid restriction limits; provide high-fiber foods; instruct patients on high water content foods; monitor bowel function; encourage increased mobility within tolerance; sparingly encourage laxatives and enemas.

• Deficient knowledge: Explain rationale for thyroid hormone replacement; describe the desired effects of medication and develop a schedule and checklist for self-administration; describe signs and symptoms of overdose/underdose; explain the need for long-term follow-up.

• Ineffective breathing pattern: Monitor respiratory rate, depth, pattern, oxygen saturation, and arterial blood gases; encourage deep breathing and coughing; use incentive spirometry; administer medications (hypnotics/sedatives) carefully; maintain patent airway.

• Other information regarding specific patient situations is addressed (e.g., myxedema, exophthalmos).