The treatment of hypothyroidism with levothyroxine is guided by labwork.  You may have heard that treatment is based on symptoms or resolution of symptoms.  Though, it is important to note any changes in the symptom, the dose of the medication is mostly guided by your lab results.   There are several reasons for this.  First, the symptoms may not be related to hypothyroidism.  They may not resolve with treatment or normalization of the labs.  Increasing the dose based on symptoms alone may cause the levels to swing to the other extreme and cause hyperthyroidism.  The organs and body are seeing too much thyroid hormone and most likely will develop new problems such as difficulty sleeping, concentrating, growth issues, increased heart rate, sweating, and increased stool frequency.

In general there are guidelines on increasing the dose such that the levels the TSH is the low end of normal but not suppressed and the ft4 is at the upper end of normal.  In individuals who do not have a disorder of hormone production from the hypothalamus or pituitary the treatment goals are based on the thyroxine levels.

What medication to use?  Levothyroxine is the recommended medication.  It is given in tablet form and can be crushed for those children that are too young to swallow the tablet whole.  

Generic vs brand?  In general both generic and brand names contain the same active ingredient or medication but have different inactive ingredients.  Brand name medications cost more than generic medications.  Brand name medications pharmacokinetics though maybe different or have more reliable dosing.  In some instances, such as severe congenital hypothyroidism it might be recommended that brand name medication such as Synthroid be used instead of generic. 

Levothyroxine vs liothyronine?  Levothryoxine is activated into the active form or triiodothyronine.  In majority of individuals, providing thyroid hormone replacement in the form of levothryoxine will treat the hypothyroidism effectively.  In rare cases, your physician may determine that there maybe a benefit from adding T3 supplementation.

Dessicated thyroid hormone?  Desiccated thyroid hormone in not FDA approved to be used in in pediatric patients.  The pills do not have consistent dosing as they are derived from dried animal thyroid glands.  Each batch had different amounts of T4 and T3 making it harder to get the blood levels into the normal range.

Generic Levothyroxine Compared with synthroid in Young Children with Congenital Hypothyroidism. JCEM 2013

Carswell, J. M., Gordon, J. H., Popovsky, E., Hale, A., & Brown, R. S. (2013). Generic and Brand-Name l-Thyroxine Are Not Bioequivalent for Children With Severe Congenital Hypothyroidism. The Journal of Clinical Endocrinology and Metabolism, 98(2), 610-617.

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