Hypothyroidism is the most common hormonal deficiency worldwide and is managed mainly by primary care physicians (PCPs).1 In a meta-analysis of European studies, the prevalence of undiagnosed hypothyroidism was 4.9%, while the prevalence of known hypothyroidism was clearly lower (3.1%).2 Another study carried out specifically in primary care in Spain3 showed that 8.8% of the general population suffered from hypothyroidism. This frequency was clearly higher in women (13.3%) than in men (4.2%) and raised as the age of the subjects studied increased.

Various international4–6 and national guidelines7 offer recommendations for the screening, diagnosis, and treatment of hypothyroidism. Despite this, many studies have found that 40–50% of patients receiving levothyroxine (L-T4) are poorly controlled due to either under- or overtreatment.8–11

The proper management of this common disease by PCPs is essential to achieve an accurate diagnosis and treatment and avoid comorbidities associated with excess or defect of thyroid hormone. In recent years, several studies dealing with the adherence of patients to replacement treatment and the opinion of patients on their disease, have been reported.12–18 Other investigations have evaluated diagnostic and therapeutic attitudes in primary hypothyroidism by endocrinologists,16,19,20 and two studies have included endocrinologists and general practitioners in France21 and the United States.22 However, we did not find any study investigating this topic in Spain. Therefore, we aimed to document the current practices of PCPs in the management of adult patients with primary hypothyroidism in Madrid (Spain).

Thyroid dysfunction screening by measurement of serum TSH is a matter of international debate.24–26 Our survey results show that Madrid's PCPs show a high level of awareness of hypothyroidism and agree with these general recommendations. Interestingly, some societies recommend screening in subjects over 50–60 years of age, especially in women.26,27 However, only 48.0% and 65.2% of the respondents agreed with screening men and women, respectively, over 60 years of age. It is noteworthy that 71.1% of PCPs were favourable to detecting hypothyroidism in diabetic patients, as has been proposed by some authors.28–30

Most of the respondents requested a second TFT determination, antibody testing, and lipid panel in both SH and OH diagnostic evaluation. Thyroid US is not recommended routinely in hypothyroid patients in current guidelines.5,31 Nonetheless, it is striking that 27.1% of respondents requested this study in patients with SH and 69.6% in patients with OH. In addition, those with more than 25 years of practice are more likely to request thyroid US. This may reflect an increased presence of US devices in primary care centres, or a greater interest of the PCPs to evaluate the presence of thyroid nodules or Hashimoto's thyroiditis in these patients.

Patients with SH and TSH values in the 5–10mU/l range represent a subset in which treatment with thyroid hormone is controversial.5 Remarkably, more than 50% of respondents treat mild SH (TSH levels 5–10mU/l) because of the presence of symptoms with the expectation that symptoms may improve. Many physicians also use the presence of antibodies to decide the treatment of SH, but guidelines only recommend using thyroid antibodies for investigating the cause of hypothyroidism and not for the decision to start treatment.5

In general, we observed a tendency to overtreatment of SH since only 22.1% of respondents stated that they do not treat SH with TSH of 5–10mU/l. This agrees with a trend toward a lower threshold for treating SH reported in United Kingdom32 and Denmark.33 However, this overtreatment might cause a significant proportion of patients treated with thyroid hormone to be in a situation of subclinical thyrotoxicosis, as has been shown by some studies.8–10,34,35

Most PCPs offer appropriate advice to their patients on how to take the tablets. Brand name preparations of L-T4 was preferred by 64.7% of PCPs, in contrast to 49.9% of endocrinologists in the survey by Burch et al.19 and to 83% of ATA members in the survey by McDermott et al.22 Starting therapy with FRD is safe in otherwise healthy individuals.22,36 However, the gradual rate of replacement, starting with low doses, was the option chosen by 67.3–94.2% of PCPs, according to the age of the patients. This gradual rate of replacement has been reported in half of the patients studied by Delemer et al.,21 and was the option chosen by 38.5% of endocrinologists in the survey of Burch et al.19 Starting therapy with FRD in young patients was more common among specialists than among PCPs in the survey of McDermott et al.22 Our survey did not include any questions about the use of different L-T4 formulations, such as liquid solution or soft-gel capsules, as the only L-T4 available in Spain is in tablet form.

Contrary to the opinion of endocrinologists in previous studies,19,22 a target of TSH in the lower half of IoR was an option scarcely chosen by our respondents, even in young patients (25.3% in patients <45 years). As previously shown,22 PCPs often chose a broader TSH goal in patients of all ages, and it seems that they are not comfortable with a TSH target in the lower half of the IoR.

Rechecking TFT after starting therapy was performed between 1 and 3 months by 98.0% of respondents. It is striking that, apart from serum TSH, many respondents also request determinations not recommended by guidelines (FT4) or not helpful in monitoring (FT3 and antibodies).5 After achieving stable TSH values, 68.7% of respondents obtained laboratory studies yearly and 31.0% at 6-months intervals. In contrast, 34.0% and 55.5% of endocrinologists performed monitoring every 12 and 6 months, respectively.19 Although some studies have shown a transient suppression of serum TSH levels after L-T4 dosing,37 only 27.8% of respondents recommended blood sampling for TSH before L-T4 ingestion.

Symptoms of hypothyroidism are not specific, and each of the symptoms generally associated with hypothyroidism may also have non-thyroid causes.38 In our survey, 61.4% of respondents performed testing for other sources of the patient's symptoms, in contrast to 84.3% of endocrinologists.19 It is noticeable that 48.9% of family doctors refer these patients to the specialist. As recommended by guidelines4,6 the use of T3-containing therapies was anecdotic.

Our data suggest that a longer professional practice time is not always accompanied by better adherence to guideline recommendations. This could be the case for the use of US in diagnosis and the preference for FRD in patients older than 65 years. Surprisingly, PCPs less prone to treat their patients and more favourable to refer to the specialist patients with persistent symptoms have more professional practice time.

We believe our results are likely to represent current practices in primary care in Madrid since the survey was answered by 14% of PCPs. This percentage is in line with that obtained in other studies on hypothyroidism. In the survey by McDermott et al.,22 the response rate was 24% of the invited PCPs. In the study by Delemer et al.,21 9.5% of the PCPs agreed to participate. In the report by Burch et al.,19 10.9% of the members of the Endocrine Society responded to the survey. Moreover, the distribution by geographic areas of the responding PCPs from Madrid was regular, and there was no health area with less than 10% of respondents.

Furthermore, most of the respondents answered all the questions on the survey, and there were very few unanswered questions. The study was limited to Madrid; therefore, results cannot be extrapolated to other geographical regions. It is possible that PCPs who are more interested in hypothyroidism may have been more willing to respond to the survey than other physicians. In addition, results may be biased by this fact, that is, the management of hypothyroidism by such a group of dedicated doctors could differ significantly from that of the average physicians. To settle this point, a new study may be needed to eliminate any doubt about the existence of such bias. The relationship and communication of PCPs with the Endocrinology departments of Madrid's different health areas was not analysed in this study. It is possible that these relationships are different in the various areas and that, therefore, this may condition differences in the management of hypothyroidism.

In summary, the present report shows that the management of hypothyroidism by the Madrid PCPs broadly follow the recommendations of the international guidelines. However, PCPs tend to deviate from the recommendations due to the widespread use of thyroid US and thyroid antibodies, the criteria for starting therapy of SH and the definition of TSH targets according to age.

The data are available from the corresponding author upon request.

The study received favourable reports from the Research Ethics Committee of the Hospital Universitario Puerta de Hierro Majadahonda and the Central Research Committee of the GAAP (code 37/19).

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