HYPOTHYROIDISM

 

Mauro Czepielewski, MD., Ph.D. in Endocrinology – São Paulo State University School of Medicine (UNIFESP). Vice-Director of the State University Rio Grande do Sul School of Medicine (UFRGS). Associate Professor – Internal Medicine Department/UFRGS.

 

What is it?

A number of signs and symptoms arising from a decrease in thyroid hormones.

How does it develop?

It’s a clinical condition that occurs due to the deficit of thyroid hormones resulting from several thyroid diseases.

In neonates, the most frequent causes involve:
 

absence of formation of the thyroid gland (embryonal defects),
hereditary defects of the enzymes that synthesize the hormones, or
diseases and drugs taken by the mother that interfere with the functional activity of the infant’s gland.

In adults, the disease may be caused by:
 

autoimmune disorder (Hashimoto’s thyroiditis),
following thyroid removal surgery for nodular goiter or neoplasia,
drugs interfering with the synthesis and release of the thyroid hormones (amiodarone, lithium, iodine),
or, more rarely, endemic goiter resulting from dietary iodine deficiency.

What does one experience?

In neonates, there is:
 

hoarse cry,
umbilical hernia,
constipation,
apathy,
decreased reflexes,
dry skin,
impaired development.

In the event that the patient doesn’t receive suitable treatment until he/she is four weeks old, severe mental retardation, deafness, and delayed development of weight and height may occur.

In children, the disease may cause growth deficit associated with:
 

dry skin,
drowsiness
attention deficit
constipation,
cold intolerance, and
apathy

In adults, symptoms are:
 

cold intolerance,
drowsiness, constipation,
swellings in the body’s extremities and eyelids,
appetite reduction,
modest weight gain
muscle weakness,
slow mental activity,
depression,
dry, brittle, slow-growing hair
dry, brittle, slow-growing fingernails
fallen eyelids, and
hair loss.

The disease prevails in the female gender, in which menstrual irregularity also occurs, including stoppage of menstrual periods (amenorrhea), infertility, and galactorrhea (appearance of milk in the breast outside the gestational period and puerperium).

When the disease is of autoimmune cause (Hashimoto’s thyroiditis), vitiligo and association with other autoimmune disorders may happen:
 

Endocrine (diabetes mellitus, adrenal gland insufficiency, hypoparathyroidism)
Systemic (candidiasis, autoimmune hepatitis)

How does the doctor diagnose it?

In the neonate, a neonatal filter paper screening must be performed for T4 or TSH levels. If these levels are changed, the test must be confirmed with the same procedures in the blood, and if changed, treatment must start at once.

In the adult, the diagnosis is established by T4 and TSH levels, and if these are changed (low T4 and elevated TSH), the underlying cause must be investigated by a study of antithyroperoxidase (anti-TPO) antimicrosomal antibodies or antithyroglobuline, which will demonstrate the autoimmune cause of the disorder. In patients with previous surgery, in addition to antibodies, a study of the remaining thyroid tissue can also be conducted by ultrasound or thyroid scintillography. The patient’s lipid profile must also be assessed, since severe dyslipidemia occurs in association with the hypothyroidal state.

How is it treated?

The treatment for all forms of hypothyroidism is performed with Thyroxine (T4) in calculated doses of 1.6 and 2.2 mg/kg bodyweight in the adult and 3 to 15 mg/kg bodyweight, depending on patient age. Treatment management is carried out by TSH levels, which must always be kept normal. In dyslipidemia patients, cholesterol and triglyceride levels must be monitored as well.

How is it prevented?

Cases occurring postoperatively can be prevented by an adequate surgery at the time surgery is indicated for goiter treatment. In other situations, an early diagnosis can be made; however, primary prevention is not available.

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