People without a thyroid can live the duration of a standard human life as long they take prescribed thyroid hormone medication, as stated by the MedlinePlus. A person without a thyroid may need to take medication for his entire life to maintain thyroid hormone levels.
Symptoms may occur for people missing a thyroid gland who fail to take thyroid hormone replacement, according to About.com. The symptoms for irregular thyroid hormone levels include fatigue, depression, memory loss, joint or muscle pain, increased risk of heart disease, myxedema coma and death. Thyroid medication may take weeks or months to show noticeable effects. If the medication does not take effect after several months, a dosage adjustment may be necessary.