Hypothyroidism

Suboptimal levels of thyroid hormones in the body results in hypothyroidism.

• This commonly occurs in patients with overcorrection of previous hyperthyroidism treated with radioiodine, antithyroid medications, or thyroidectomy.
• It more often occurs in older women, and also by virtue of thyroid cancer experienced by men who have undergone radiation therapy for head and neck cancer.
• Myxedema, a dermatologic condition found in severe hypothyroidism, is a state where an accumulation of mucopolysaccharides in subcutaneous and other interstitial tissues occur (generalized edema). (Myxedema is also sometimes used interchangeably with severe hypothyroidism)

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Classifications

• Primary/Thyroidal Hypothyroidism: failure of the thyroid to produce adequate thyroid hormones. This is found in ~95% of patients with hypothyroidism.
• Central Hypothyroidism: failure of the pituitary gland and/or the hypothalamus to stimulate the production of thyroid hormones.
• Secondary/Pituitary Hypothyroidism: an entirely pituitary disorder, leading to decreased TSH secretion, and subsequent decreased T₃ and T₄ production.
• Tertiary/Hypothalamic Hypothyroidism: a hypothalamic disorder wherein thyrotropin-releasing hormone (TRH) is not produced, and the release of TSH is inhibited, resulting in decreased T₃ and T₄ production.

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Causes

• The most common (general) cause is thyroid inflammation, damaging the gland’s cells.
• Autoimmune diseases is the most common cause of hypothyroidism in adults (autoimmune thyroiditis) or Hashimoto’s Disease.
• Thyroid Atrophy occurs naturally when aging.
• Hyperthyroidism Therapy may result in hypothyroidism, such as in radioiodine therapy, and thyroidectomy.
• Medications such as lithium, iodine compounds, and antithyroid medications decrease TSH production.
• Iodine Deficiency: iodine is an essential component of thyroid hormones.
• Iodine Excess: iodine saturation results in suppression of thyroid hormone production (inhibition of thyroid peroxidase) as a protective mechanism against hyperthyroidism (Wolff-Chaikoff Effect).

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Complications

• Myxedema Coma: a decompensated state of severe hypothyroidism in which the patient becomes hypothermic and unconscious.

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Assessment Findings

1. Extreme Fatigue: due to hypometabolism
2. Menstrual Disturbances (Menorrhagia, Amenorrhea): thyroid hormones have complex interrelationships with reproductive hormones and function.
3. Weight Gain: due to hypometabolism
4. Cold Intolerance: decreased body heat results in intolerance to cold environments.
5. Thick Skin: generalized accumulation of mucopolysaccharides in subcutaneous tissue results in the thickening of the skin.
6. Irregular Thyroid Gland: palpation of they thyroid gland is routine. Enlargement or atrophy should be noted.

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Diagnostic Examination

1. Physical Examination: palpation of the thyroid gland in all patients.
2. Serum TSH Test: the single-best screening test for thyroid function due to its high sensitivity. Normal TSH levels are 0.5 to 1.5 mU/L.
3. Serum Thyroid Hormones Tests include both protein-bound and free hormone levels in response to TSH secretion.
4. Thyroid Antibody Testing: immunoassay techniques look for antithyroid antibodies which are active in all case of Hashimoto’s Thyroiditis.

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Medical Management

The primary objective is to restore normal metabolic status through hormone replacement. Prevention of complications and supportive therapy are included.

1. Pharmacologic therapy: Synthetic Levothyroxine is the preferred preparation for hypothyroidism and suppression of non-toxic goiters.
2. Prevention of Cardiac Dysfunction: subnormal metabolism result in decreased oxygen requirements. Reductions in blood supply may be tolerated without overt symptoms, but coronary artery disease may become evident once metabolism is restored to normal status.
3. Supportive Therapy: oxygen saturation is monitored, fluids are administered cautiously (due to fluid retention), external heat application should be avoided, and oral thyroid hormone therapy should be continuous.

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Nursing Interventions

Assessment

• Palpation from an anterior and posterior position, assessing for any abnormalities, firmness (Hashimoto’s) or tenderness (thyroiditis)
• Auscultation of the thyroid gland if any abnormalities are palpated.

Diagnoses and Interventions

• Activity Intolerance related to decreased physiological and psychological energy
  • Promote rest and self-care activities.
• Risk for impaired thermoregulation
  • Provide thermoregulation precautions: blankets, no external heat sources, temperature monitoring, avoiding exposure to drafts, etc.
• Constipation related to decreased gastrointestinal peristalsis
  • Encourage fluid and dietary fiber intake. Mobility should be encouraged within tolerable limits, and use of laxatives or enemas should be used sparingly. Monitor bowel activity.
• Impaired breathing associated with depressed ventilation.
  • Assess respiratory parameters (depth, rate, pattern, oximetry, ABG)
  • Encourage deep breathing, coughing, and incentive spirometry.
  • Verify any hypnotics or sedatives being ordered. If necessary, monitor for adverse side effects.
  • If necessary, suctioning and mechanical ventilation may be done.
• Acute confusion associated with altered cardiovascular and respiratory status and depression.
  • Orient the patient to the four spheres: person, place, time, situation

Discharge Education

1. Medication Compliance: emphasis of compliance with life-long therapy.
2. Thermoregulatory Precautions: avoid extreme cold until condition is stable.
3. Follow-up Care: state the importance of follow-up care.
4. Weight Reduction Strategies and Prevention of Constipation: identify strategies with the patient e.g. a high-fiber, low-calorie and adequate fluid diet.