Transient hypothyroidism, as the name suggests, is a temporary type of hypothyroidism that can affect both adults and new born infants.
Transient Congenital Hypothyroidism In Newborns
Transient congenital hypothyroidism is transient hypothyroidism in new born babies, notably premature and low birth weight infants, and is more common than you’d expect. Around 10 to 20% of new born infants have this type of hypothyroidism but most are producing normal levels of thyroid hormone by the time they’re several months old.
The most common causes of transient congenital hypothyroidism are:
- Too much iodine
- Too little iodine
- Transfer of thyrotropin receptor blocking antibodies from the mother during gestation
- Maternal use of anti-thyroid drugs during gestation
A study in Italy found that in half of infants diagnosed with transient hypothyroidism the culprit was excessive exposure to iodine either in utero or at birth. An iodine rich medication called amiodrarone is used to regulate heart rhythm. If either the mother, or the fetus, are given this it can disrupt thyroid function in the unborn infant. Other sources of iodine that have the ability to interrupt neonatal thyroid function include use of iodine based disinfectants (ie povidone) during the birthing process, for treating the umbilical stump, and disinfecting skin (injection sites, surgery). Further to this, an iodinated contrast substance may be injected to highlight major veins so they show up on radiographic equipment.
Insufficient iodine can also cause transient hypothyroidism in new born infants. Premature babies are especially susceptible to this due to an immature HPT axis that is unable to produce enough thyroid hormone. They also have a reduced capacity to convert T4 to T3.
A third of the cases in the Italian study were attributed to placental transfer of maternal TSH receptor blocking anti-bodies during pregnancy. Notably this occurs in mothers that have some form of autoimmune thyroid disease themselves. These anti-bodies block the TSH receptors in the baby’s thyroid gland, preventing it from producing its own TSH. This type of transient congenital hypothyroidism begins to correct itself between 3 and 6 months as the mother’s anti-body levels reduce.
Some anti-thyroid drugs may also cause transient hypothyroidism in the fetus if they cross the placenta during fetal development. The drop in the infant’s thyroid hormone production is usually short-lived – from a few days to a few weeks after birth. However, in severe cases it can cause the thyroid glands to become enlarged to the point where they affect the baby’s airways.
Interesting Questions about Thyroid:
When are thyroid hormone pills used?
Thyroid hormone pills provide the body with the right amount of thyroid hormone when the gland is not able to produce enough by itself. The pills are frequently needed after surgery or radioactive iodine therapy.
Thyroid hormone tablets are the standard treatment for hypothyroidism. While symptoms usually get better within a few months, most patients must take the pills for the rest of their lives. This is especially true for hypothyroidism caused by Hashimoto’s thyroiditis or radioactive iodine treatment.
If the entire thyroid gland has been surgically removed, thyroid hormone tablets replace the body’s own source of the hormone. If only a part of the gland has been removed, the pills may keep the remaining gland from working too hard. This decreases the chance that the thyroid gland will grow back.
How much hormone do I need?
The preferred hormone for treatment is levothyroxine (T4). You should use only the brand-name that your doctor prescribes, since generic brands may not be as reliable. Name-brand levothyroxine pills include Synthroid®, Levoxyl®, Levothroid®, Euthyrox®, and Eltroxin®.
Patients sometimes take more pills than they should, trying to speed up the treatment or lose weight. However, this can lead to hyperthyroidism and long term complications, such as osteoporosis. You should take the pills as your doctor prescribes.
At different times in your life, you may need to take different amounts of thyroid hormone. Therefore, you should see your doctor at least once a year to make sure everything is all right.
® Synthroid is a registered trademark of Knoll Pharmaceuticals.
® Levoxyl is a registered trademark of Jones Medical Industries.
® Levothroid is a registered trademark of Forest Pharmaceuticals.
® Euthyrox is a registered trademark of EM Pharma.
® Eltroxin is a registered trademark of Roberts Pharmaceuticals.
Are thyroid hormone pills needed after treatment for hyperthyroidism?
Many patients treated for hyperthyroidism become hypothyroid. They will need to take thyroid hormone pills for the rest of their lives. In addition, they will need to see their doctor at least once a year.
Hyperthyroidism from any cause can make the upper eyelids pull back, but Graves’ disease often causes one or both eyes to bulge out of their sockets. This condition, known as exophthalmos, can cause loss of eye muscle control, double vision, and (rarely) loss of vision. Most cases require no treatment, but some patients may need to see an eye doctor (ophthalmologist) for specialized treatment. This may include steroids, radiation, or surgery.
When are beta-blocking drugs used?
Beta-blocking drugs, also called beta blockers, treat the symptoms of hyperthyroidism. They do not significantly affect the gland or the levels of thyroid hormones in the blood. Instead, they “block” the effects of thyroid hormones.
Beta blockers are most useful for patients whose hyperthyroidism makes them uncomfortable. High hormone levels can cause a faster heart rate and trembling. Beta-blocking drugs help control these symptoms.
Beta-blocking drugs should not be used by patients with asthma.
Have more questions? Need more answers? Check our Full Thyroid FAQ
Diagnosing Transient Hypothyroidism In Newborns
In most developed countries advanced newborn screening (NBS) programs done between 2 and 4 days of age will now pick up thyroid abnormalities, allowing for appropriate treatment as required. Where such programs are not available the effects of transient congenital hypothyroidism are usually not seen until several weeks after birth because the infant is temporarily protected by maternal thyroxine received during gestation. However, as this thyroxine drops away deficiencies in the infant’s own thyroid will start to become apparent.
Clinical symptoms of transient congenital hypothyroidism include:
- blotchy skin
- blue or purple skin around the mouth (perioral cyanosis)
- breathing problems
- difficulty feeding
- floppy baby syndrome (hypotonia)
- hoarse crying
- lack of movement
- lingering jaundice (icterus)
- noticeably pale skin
- swelling around the eyes (periorbital edema)
Typical physical manifestations of transient congenital hypothyroidism:
- narrow forehead
- unusually large soft spots (fontanelles)
- sunken nasal bridge
- puffy eyelids (periorbital edema)
- swollen tongue
- cold, dry and thickened skin
- a lot of long coarse hair
- umbilical hernia
- low blood pressure (hypotension) with narrow pulse pressure
- abdominal distention associated with anemia
- lack of reflexes or poor reflexes (hyporeflexia)
- slow heart beat (bradycardia)
As babies can also be born with either permanent congenital hypothyroidism or secondary or central hypothyroidism, the first step with infants diagnosed with thyroid abnormalities is to establish what type they have. Infants returning results consistent with either of these will be started almost immediately on thyroid medications and will continue to require these for the rest of their lives. Those with NBS results strongly indicative of transient hypothyroidism are usually re-screened after a couple of weeks and if hormone levels are within normal range will not generally require any treatment.
Those who are still abnormal ie showing high TSH levels, will be started on thyroxine treatment to prevent brain abnormalities but will be re-assessed at 3 years of age. This is due to the fact that with these cases, at this age, it’s almost impossible to determine whether they have the transient or congenital form of the disease. Therefore treatment is started as a preventative because elevated TSH levels persisting beyond 4 weeks of age affects the development of the brain.
For more information about treatment options for infant hypothyroidism based on results of NBS testing visit this link.
Transient Hypothyroidism In Adults
Transient hypothyroidism (thyroiditis) in adults usually occurs after some type of trigger causes a temporary reduction in thyroid hormone production resulting in hypothyroidism-like symptoms:
- immune reaction (silent thyroiditis)
- pregnancy and child birth (postpartum thyroiditis)
- infection (subacute thyroiditis)
- thyroiditis caused by TSH receptor-blocking anti-bodies
In most cases, thyroid function returns to normal after a period of time with treatment. However, in some cases it may become permanent hypothyroidism.