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What is hypothyroidism and how is it treated?

Camille C. Irizarry Vega's picture

Before I started studying pharmacy, my mother used to tell me often that she did not feel quite right, she was always tired and had been recently gaining some weight without any apparent trigger or change in eating habits. It never occurred to me that these symptoms were the onset of hypothyroidism. After being diagnosed, my mother joined the number of people suffering from the thyroid, along with my grandmother and grandfather and many other Puerto Ricans.  

Hypothyroidism is more common than we think.  According to the American Thyroid Association (ATA), approximately 20 million Americans suffer from a thyroid disorder. Of these, 60% do not know that they suffer from the condition.

In Puerto Rico, several studies have been conducted on the prevalence of hypothyroidism.  One of these, by Figueroa (2008), identified a prevalence of hypothyroidism of 8.2% in a group of overweight people over 21 years of age.  According to Molina et. al. (2007), among a group of patients with lupus, the prevalence of hypothyroidism was 19%. Finally, according to González et. al (2013), the prevalence in a group of postmenopausal women was 24.4%.

Hypothyroidism is observed more in women than in men and that the risk of suffering from it increases with age. This is why I have given myself the task of sharing more information about this condition in the official thyroid awareness month.

It should be noted that hypothyroidism is not the only thyroid disorder that exists.  The thyroid is a gland located in the front of the neck that produces the hormones T3 (triiodothyronine) and T4 (thyroxine). These, in turn, regulate other functions of the body and affect metabolic processes through their effect on various organs.

Hypothyroidism is a deficiency in the production of hormones T3 and T4 which causes an imbalance in metabolic functions. As a result of the decrease in the production of these hormones, the characteristic symptoms of hypothyroidism begin to manifest in the body.   

There are certain populations that are at a higher risk of suffering from hypothyroidism.  Among these are women post-pregnancy, people with a family history of autoimmune disorders of the thyroid, people with endocrine conditions (diabetes mellitus type 1, adrenal insufficiency, among others), multiple sclerosis, Down syndrome, and pulmonary hypertension, among others.

What is the clinical presentation of a typical patient with hypothyroidism? It is important to highlight that every patient is different and the symptoms can vary or manifest themselves in different ways in different patients.  A symptom is a manifestation of a disease that is perceived by the person who suffers it, while a sign is an obvious manifestation noticed by an observer who is not the patient.

Some of the most common symptoms are the following:

  • Dry skin
  • Cold intolerance
  • Weight gain
  • Constipation
  • Weakness
  • Abnormalitiesmenstruation (women)
  • Hair loss

Some of the signs are the following:

  • Reduced cardiac pulse
  • Hoarse voice
  • Fluid retention
  • Swollen face, hands, and feet


The diagnosis of hypothyroidism is made taking into account the levels of the thyroid stimulating hormone (TSH) and those of the already mentioned, T3 and T4.  A typical patient with hypothyroidism will have a high TSH value and a T4 value below the normal range.  The level of the T3 hormone can remain normal even when the T4 levels are below the normal range. These are the typical results that a patient with hypothyroidism will present but they can vary according to the patient.  

Treatment Goals

What do we want to achieve with the treatment?  The goal of treatment is to restore the normal levels of the aforementioned hormones, which will provide relief of symptoms, prevent complications and revert the metabolic imbalances of hypothyroidism.


Levothyroxine (Synthroid®) is a synthetic form of thyroxine (T4) that increases cellular metabolism and acts just like the natural hormone T4 that our body produces. Since hypothyroidism is characterized by a decrease in the production of thyroid hormones, this medication is used to replace that hormone that we are not producing in sufficient quantity. This is why levothyroxine (Synthroid®) is currently the most prescribed oral medication to treat hypothyroidism.  It is available in oral (tablets) and intravenous (IV) presentations and there are specific guidelines for switching from oral to IV administration according to the needs of the patient.

The dose of levothyroxine for each patient is calculated according to their weight and is adjusted according to the levels of the thyroid hormones in the blood and the clinical picture of the patient. This medicine can be used by pregnant women, infants, infants, children and the elderly.

All medications can cause side effects, so it is important to be aware of any changes in your body and mood and know some of the most common adverse effects.  It is essential to consult your primary doctor or endocrinologist if you experience any symptoms that may be associated with a possible adverse effect of the medication.

Some of the adverse effects that can be associated with the therapy with levothyroxine are arrhythmia, palpitations, anxiety, fatigue, headache, insomnia, irritability, excessive sweating, diarrhea, and fever. Also consider other medications you are taking, as there may be interactions between levothyroxine and other drugs. If you are taking any product that contains calcium or iron, it is important to wait at least 4 hours after the administration of levothyroxine.  Antibiotics like Cipro® can reduce absorption of levothyroxine, so it is recommended that they are taken at least 6 hours apart.

In order to monitor the efficacy of the treatment, the TSH levels should be evaluated between 4-6 weeks after the start of treatment or a change in dose regimen.  These results will determine if the medication is being effective or if the dose needs to be adjusted. Once the levels of thyroid hormones are normalized, blood tests measuring the levels of the thyroid hormones should be performed every 6 months to a yearly to confirm that the treatment is yielding the expected results.

If you have hypothyroidism and take levothyroxine, remember to take it before breakfast with a glass of water.  Let your pharmacist and doctor know all the medications you are taking (whether prescribed or not) to assess if there is any interaction that may result in adverse effects. It is also important to evaluate how you feel after starting the treatment and if it does not feel right, do not delay in consulting your doctor. Remember that your health and wellbeing comes first.

Camille C. Irizarry Vega, Pharm.Dc 2019 RCM


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  2. "General Information / Press Room | American Thyroid Association". American Thyroid Association, 2019,

  3. Jameson, J. Larry, et al .. "Hypothyroidism." Harrison's Principles of Internal Medicine, 20e Eds. J. Larry Jameson, et al. New York, NY: McGraw-Hill,

  4. Figueroa B, Vélez H, Irizarry-Ramírez M. Association of thyroid-stimulating hormone levels and body mass index in overweight Hispanics in Puerto Rico. Ethn Dis. 2008; 18 (2Supp2): S2151-S2154.

  5. Molina MJ, Mayor AM, Franco AE, Morell CA, Lopez MA, Vilá LM. Prevalence of systemic lupus erythematosus and associated comorbidities in Puerto Rico. J Clin Rheumatol. 2007; 13 (4): 202-204.

  6. González-Rodríguez, Loida et al. "Thyroid Dysfunction In An Adult Female Population: A Population-Based Study of Latin American Vertebral Osteoporosis Study (LAVOS) - Puerto Rico Site.". Puerto Rico Health Sciences Journal, 2013.