Hypothyroidism

Diagnosis/Definition

Hypothyroidism is the complex of findings that arise when the peripheral tissues are presented with and respond to inadequate levels of thyroid hormone. Disorders associated with hypothyroidism may be broadly categorized as follows:

Agenesis.
Inadequate replacement therapy.
Destruction of the gland, surgical removal, irradiation, autoimmune disease, replacement by cancer or other disease or post-thyroiditis.
Idiopathic atrophy.
Inhibition of thyroid hormone synthesis, iodine deficiency, excess iodine in susceptible patients, antithyroid drugs or inherited enzymatic defects.
Transient (occurring after surgery or radioiodine treatment, postpartum, or in the course of thyroiditis).
Central hypothyroidism, disruption of the hypothalamic pituitary and thyroid axis.

Initial Diagnosis and Management

Patients with iatrogenic hypothyroidism need not be referred. Their dose of thyroid hormone should be increased; a TSH should be measured six weeks later.
An attempt should be made to determine the etiology of the patient’s condition.
In addition to a thorough history and physical exam, anti-thyroid antibody titers may be of value. (Note: Thyroid scans and thyroid ultrasounds are not indicated in the evaluation of hypothyroidism).
Transient forms of mild hypothyroidism often do not require treatment. The patient should be reassured.
Serial (every 1-3 months) thyroid function tests (TSH and FT4) should be obtained to document resolution.

Ongoing Management and Objectives

Major objective is euthyroidism as reflected by a normalized TSH (normalized peripheral products in those patients with secondary or tertiary hypothyroidism).
Adjustments to thyroid hormone dosage should not be made on the basis of symptomatology alone.
A variety of medications and other factors may affect the bioavailability of thyroid hormone. An adjustment to thyroid hormone dosage is not reflected in the thyroid function tests for a period of six to eight weeks.
Patients over the age of 50 years or those with known or suspected coronary disease should begin replacement therapy with a low dose of medication and gradually have dose increased, e.g. levothyroxine, 0.025 mg/d starting dose with .0125mg to .025 mg increase every 2-4 weeks.

Indications for Specialty Care Referral

In general, patients with hypothyroidism are easily diagnosed and treated. They will not require subspecialty care.

Certain patients, i.e., those who appear unresponsive to replacement therapy or those with unusual forms or manifestations of hypothyroidism may require referral.

Patients with central hypothyroidism should be referred for assessment.

Criteria for Return to Primary Care