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 Table of Contents  
Year : 2015  |  Volume : 2  |  Issue : 1  |  Page : 19-27

Prevalence of thyroid dysfunction in gestational hypertensive Nigerians

Department of Chemical Pathology, Aminu Kano Teaching Hospital, Bayero University, Kano, Nigeria

Date of Submission15-Oct-2014
Date of Acceptance20-Jan-2015
Date of Web Publication17-Feb-2015

Correspondence Address:
Kabiru Abdulslam
Aminu Kano Teaching Hospital, Bayero University, Kano
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2384-5147.151569

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Background: Thyroid physiology changes significantly during pregnancy. Consequently, thyroid disorders are prevalent in women of child-bearing age and commonly present in pregnancy and puerperium. Untreated thyroid dysfunction in pregnancy has adverse effects on fetal and maternal well-being, including miscarriage, placental abruption, preterm delivery and preeclampsia. Aim: The aim of this study was to determine the prevalence of thyroid dysfunction among patients with gestational hypertension in Nigeria. Materials and Methods: Plasma concentrations of thyroid stimulating hormone, free thyroxine, and free tri-iodothyronine (fT 3 ) were measured in 165 pregnant women (aged 18-40 years) with gestational hypertension and 126 age-matched normotensive pregnant women, who served as controls. All laboratory analyses were conducted on Elecsys 2010 immunology analyzer, using a highly sensitive and specific chemiluminescence immunoassay method. Results: The prevalence of thyroid dysfunction was 23.6% and 10.3% in women with gestational hypertension and the normotensive pregnant women respectively. The most common thyroid dysfunction among the study participants was subclinical hypothyroidism accounting for 41.0% and 46.2% of all cases of thyroid abnormalities among the gestational hypertensive women and their normotensive counterparts, respectively. Conclusion: In view of the relatively high prevalence of thyroid dysfunction found in this study, it is suggested that all pregnant women (especially those with gestational hypertension) should be routinely screened for thyroid function abnormalities.

Keywords: Gestational hypertension, thyroid function, thyroid dysfunction, pregnancy, maternal mortality

How to cite this article:
Abdulslam K, Yahaya IA. Prevalence of thyroid dysfunction in gestational hypertensive Nigerians. Sub-Saharan Afr J Med 2015;2:19-27

How to cite this URL:
Abdulslam K, Yahaya IA. Prevalence of thyroid dysfunction in gestational hypertensive Nigerians. Sub-Saharan Afr J Med [serial online] 2015 [cited 2023 Sep 23];2:19-27. Available from: https://www.ssajm.org/text.asp?2015/2/1/19/151569

  Introduction Top

Gestational hypertension is one of the major causes of both maternal and perinatal morbidity and mortality, thereby complicating about 5-10% of all pregnancies worldwide. It is defined as blood pressure of at least 140/90 mmHg of onset or first recognition during the index pregnancy in a previously normotensive woman. [1]

Nigeria has maternal mortality ratio of 550/100,000 live births, a figure that is much higher than what is obtainable in other developing countries of the world. [2]

Though the exact etiology of gestational hypertension remains elusive, there are, however, several factors that may probably contribute to the rise in blood pressure during pregnancy. These factors include among others, an expansion in total plasma volume of up to 40%, an increase in the red cell mass of about 25%, and 25% increase in the glomerular filtration rate, and increase in the synthesis of thyroid hormones. [3],[4]

The levels of thyroid hormone transport proteins (thyroxine binding globulin, albumin and thyroxine binding prealbumin) also undergo remarkable changes during the course of a normal pregnancy. These changes are largely due to increased hepatic synthesis and decreased catabolism by both the liver and to a lesser extent by the renal tubular cells. Thyroxine binding globulin increases by about 2.5 times resulting in corresponding increase in the plasma levels of thyroxine by about 40-100%. The levels of both T 4 and T 3 thus gradually increase from conception and reach a plateau by 20 weeks of gestation and remain unchanged until term. The free hormones (free thyroxine [fT 4 ] and free tri-iodothyronine [fT 3 ]) however, remain within reference limit or slightly raised. [5]

The levels of thyroid stimulating hormone (TSH) generally decrease during pregnancy especially in the first trimester, this is largely due to a marked increase in the serum levels of human chorionic gonadotrophin, a placental hormone with alpha (α) chain similar to the alpha chain of TSH, and thus provide positive interference in TSH estimation. [6],[7]

In women generally, thyroid associated endocrinopathies are the second most common endocrine disorders after diabetes mellitus. These disorders are 4-5 times more prevalent in women during their reproductive ages and may likely be more frequent in those with other co-morbid conditions such as gestational hypertension. [6]

Due to the profound biochemical changes in pregnancy associated with significant increase in both total thyroxine and tri-iodothyronine with the free hormones as well as trimester-specific differences in the levels of thyroid hormones, the American Thyroid Association (ATA) and the British Endocrine Society (BES) advocate the use of free hormones and trimester-specific reference intervals in the screening, diagnosis and monitoring of thyroid function abnormalities in pregnancy and postpartum. [8],[9],[10]

Several studies have documented varying associations between thyroid function abnormalities and gestational hypertension. These studies were conducted in different populations and countries with varying racial, socioeconomic, and cultural differences. In the West African sub-region and Nigeria in particular, there were few studies conducted in this area. Researchers in Jos, North central Nigeria, studied the thyroid function of 32 pregnant women and compared them with those of healthy nonpregnant controls. Subclinical hypothyroidism and small for date babies were found in 15.2% and 9.8% of pregnant women from iodine-deficient and iodine-replete regions respectively. Some of the pitfalls noted in these studies included limited sample size and free hormones were not assayed in the study participants. [11]

Clinical and biochemical evaluation of the thyroid functional status of pregnant women may serve as additional prognostic and diagnostic tools that may provide some insights into the etiology and pathophysiology of gestational hypertension.

The aim of this work was, therefore, to determine the prevalence of thyroid dysfunction among patients with gestational hypertension in Kano, North West Nigeria.

  Materials and methods Top

The study was a descriptive cross-sectional study conducted over a 6-month period at the antenatal clinic of Aminu Kano Teaching Hospital, Kano, Nigeria.

The participants were made up of 165 pregnant women (aged 18-40 years) with gestational hypertension and 126 age-marched normotensive pregnant women as controls. Simple random sampling technique was used to select all the participants from the study population.

Inclusion Criteria

Patients with hypertension diagnosed after 20 weeks of gestation were included in the study. Gestational age of each of the participants was determined using the participants' last menstrual period, confirmed by ultrasonography performed during the first trimester. Age-and trimester-marched normotensive pregnant women were enrolled as controls.

Exclusion Criteria

Patients with hypertension predating the index pregnancy, those with suspected or established thyroid disease, diabetes mellitus, multiple gestation, polyhydramnios and those with antenatal booking weight of at least 90 kg were excluded from the study. Patients with history of smoking and alcohol ingestion as well as those who refuse to consent were also excluded. All patients with proteinuria of at least 2 + were equally excluded from the study.

Ethical Consideration

Ethical approval for this study was obtained from the Ethical and Scientific Committee of Aminu Kano Teaching Hospital, Kano.

In line with the Helsinki Declaration, informed written consent was obtained from the participants before the collection of data and blood samples.

Data Collection Methods

The biodata of all study participants were obtained using a structured interviewer administered pretested questionnaire. Blood pressure of each participant was measured by the investigators from the sitting position using Accoson mercury sphygmomanometer. Korotkoff's sound phases I and V were used to determine the systolic and diastolic blood pressures (SBPs and DBPs) respectively. Values above 140 and 90 mmHg for the SBP and DBP respectively were considered abnormal. Based on the blood pressure recordings, participants were further classified using the seventh Joint National Committee (JNC VII) criteria [12] as shown in [Table 1].

The weight of each participant was measured in kilograms using OMRON digital weighing balance (Omron Healthcare, Kyoto, Japan). The participants' weight and height were determined without shoes and with minimal clothing. Each participant was requested to stand steadily on the digital weighing balance facing the investigator. The weight was then determined by reading directly from the screen of the weighing balance.

The height was also determined by direct reading from the height scale mounted at the booking section of the antenatal clinic of the study center.

Blood Sample Collection and Preservation

A vacutainer system comprising the needle holder, multi-sample needle and anti-coagulated evacuated container was used to collect 4 mL of whole blood specimen from each study participant. Samples were then separated by centrifugation at 1000 revolution/min for 10 min. The sera obtained were then transferred into appropriately labeled plain containers and kept frozen at −10΀C for 4 weeks before analysis. At this temperature all samples are stable, the levels of TSH and free hormones levels will not be affected for years. [13],[14] Personal protective equipment and other universal precautionary measures were observed for all procedures of sample collection, processing and analysis.

Laboratory Procedures

Plasma concentrations of TSH, fT 4 and fT 3 were determined by the investigators using a highly sensitive and specific chemiluminescence immunoassay technique on Elecsys 2010 immunology analyzer (Roche Diagnostics Mannheim, Germany).

Calibration sets 1 and 2 for TSH, fT 4, and fT 3 were used to calibrate the analyzer prior to commencement of analytical runs.

Randox quality control sera level 1 and 3 and Precicontrol Universal were included as quality control specimens during the analytical run of each batch of samples. [15],[16],[17] As the Elecsys immunoassay analyzer has the capacity to run up to 30 samples (quality controls inclusive), the study samples were assayed in eleven analytical runs or batches.

Data Processing and Statistical Analysis

The data obtained from the study questionnaire and laboratory analysis were manually entered into an excel worksheet. It was cleaned through the use of filters and triangulation and then transferred into the Statistical Package for the Social Sciences (SPSS) version 16.0 (Microsoft Corporation, Redmond, Carlifornia, USA) for further processing. Summary of descriptive statistics were obtained for the most important quantitative variables such as age, height, body mass index (BMI), serum TSH, fT 4 and fT 3 . Qualitative variables such as occupation, marital status, parity, gestational age and the status of the thyroid function (biochemical) of the participants were entered into contingency tables and the various Chi-squares were calculated. Relationships between variables were found using suitable statistical tests of significance that is paired t- and Z-test, Chi-square. A P < 0.05 was considered as statistically significant.

Definition of Study Terms

Gestational hypertension was defined according to the recommendations of the Society of Obstetrics and Gynecology of Canada and that of the JNC. This was defined as blood pressure of at least 140/90 mmHg diagnosed from the 20 th week of gestation in a previously normotensive pregnant woman. The severity of hypertension was also classified according to the JNC criteria. [1],[12]

The thyroid function profile of each study participant was interpreted using a combination of the trimester-specific reference intervals for TSH, fT 4 and fT 3 . Participants were categorized based on the definitions of euthyroidism and various forms of biochemical thyroid dysfunctions proposed by the consensus of the ATA, American Association of Clinical Endocrinology and the BES. [8],[9],[10] The reference interval for serum TSH in first, second and third trimesters were 0.1-2.5 mu/L, 0.2-3.0 mu/L and 0.3-3.0 mu/L respectively. The reference intervals of 12-22 pmol/L and 3.1-6.8 pmol/L were stated for fT 4 and fT 3 respectively. These reference intervals were used because there were no suitable local reference intervals generally and especially for pregnant women.

The participants with serum TSH outside the stated trimester-specific reference intervals and a serum fT 4 within the reference interval were categorized as having subclinical thyroid disease. The subclinical thyroid disease could be either hypothyroidism or hyperthyroidism. Participants found to have serum TSH above the trimester-specific reference interval and fT 4 within the reference interval, without clinical features were classified as having subclinical hypothyroidism. Similarly, those with serum TSH above the reference intervals and a serum fT 4 below the reference interval were classified as having overt hypothyroidism. Participants with a serum TSH of at least 10 mu/L were classified as having overt hypothyroidism regardless of their fT 4 level. In addition, participants with TSH level below the trimester-specific reference intervals were classified as having hyperthyroidism. Those with only serum TSH level below the trimester-specific reference interval and a fT 4 within the reference interval without clinical features were classified as having subclinical hyperthyroidism. Similarly, study participants found to have serum TSH below the stated reference intervals and with a fT 4 above the reference interval were classified as having overt hyperthyroidism.

  Results Top

The participants of this study were made up of 165 patients with gestational hypertension subsequently referred to as Group I and 126 normotensive pregnant women as the control group hereafter referred to as Group II.

Baseline Biodata and Biochemical Characteristics of The Study Participants

[Table 2] shows the baseline biodata and clinical characteristics of the study participants.

Group I participants had a mean age of 27.7 ± 7.8 years while Group II had a mean age of 26.9 ± 6.4 years. There was no statistically significant difference between the mean ages of the two groups (P = 0.17).

Furthermore, there were no statistically significant differences in the mean height, weight and the BMI of the two groups studied.

Majority of the individuals studied were full-time house wives while those that mentioned the term "others" as their occupation were mainly students of various institutions of higher learning and a few individuals who did not want to disclose their occupations for security reasons.

No statistically significant difference was observed in the gestational age of the two groups studied (P = 1.7). However, there were statistically significant differences in both the SBP and DBP of the two groups. The P < 0.0001 for both the SBP and DBP respectively.

The results also show that there were significant differences in the mean TSH and that of fT 4 (P < 0.004 and < 0.0001 respectively) between the two groups. However, there were no significant difference between the mean fT 3 of the two groups (P = 0.15).

Majority of the Group I participants was primigravidae while Group II participants were mostly multigravidae [Table 3].

Prevalence of Thyroid Dysfunction Among The Study Participants

The prevalence of the various forms of thyroid dysfunction in the two groups of participants is presented in [Table 4], [Figure 1] and [Figure 2]. Subclinical hypothyroidism was the commonest form of thyroid dysfunction among Groups I participants with a prevalence of 9.7%. The least common dysfunction was subclinical hyperthyroidism a prevalence of 1.2%.
Figure 1: A bar chart showing pattern of thyroid dysfunction among gestational hypertensive group

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Figure 2: A bar chart showing pattern of thyroid dysfunction among normotensive pregnant women

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Table 1: JNC VII criteria for the classifi cation of hypertension among study population

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Table 2: Baseline biodata and clinical characteristics of the study participants

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Table 3: Distribution of the study participants by parity

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Table 4: Prevalence of thyroid dysfunction among the study participants

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Similarly, the most common form of thyroid dysfunction among the Group II participants was subclinical hypothyroidism with a percentage prevalence of 4.8%. However, unlike their hypertensive counterparts, the second most prevalent form of thyroid dysfunction among the normotensive group was found to be overt hyperthyroidism.

Association Between Severity of Hypertension and Thyroid Dysfunction

Group I participants were further categorized into mild, moderate and severe hypertensives in accordance with the JNC VII criteria. The association between thyroid dysfunction and the severity of hypertension among the Group I participants is shown in [Table 5]. No significant relationship was found between the two variables, as the computed P value was greater than the alpha level of significance.
Table 5: Association between severity of hypertension and thyroid dysfunction in Group I participants

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Distribution of Thyroid Dysfunction by Gestational age Among The Study Participants

[Table 6] and [Table 7] show the distribution of the various forms of thyroid dysfunction by age among the study participants

There was a higher proportion of thyroid dysfunction during the third trimester compared to the second trimester (P = 0.007, α = 0.05, χ2 = 7.3 > 3.8) among the Group I participants, with over 75% of all forms of thyroid dysfunction being encountered during the third trimester of pregnancy.
Table 6: Distribution of different forms of thyroid dysfunction by gestational age among Group I participants

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Table 7: Distribution of different forms of thyroid dysfunction by gestational age among Group II participants

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The distribution also showed that there were more women with thyroid dysfunction during the second trimester among the Group II participants, with subclinical hypothyroidism accounting for 60% of the thyroid abnormalities.

In Summary, 39 out of the 165 participants in Group I were found to have various forms of thyroid dysfunction, resulting in the prevalence rate of 23.6%. While 13 out of the 126 participants in Group II had various forms of thyroid dysfunction, thus giving a prevalence of 10.3%. However, thyroid dysfunction encompasses both hyper- and hypothyroidism, each with both subclinical and overt forms. The findings of the study showed that subclinical hypothyroidism was the commonest form of thyroid dysfunction among the study participants, which constituted 41.0% and 46.2% of all cases of thyroid dysfunction in Groups I and II respectively.

  Discussion Top

The anthropometric parameters of the two groups studied were similar. This was due to the careful selection of the participants in accordance with the study protocols. The participants were age and trimester matched. However, Group I participants were slightly older and had higher mean age, but had lower mean height compared with Group II. This is in keeping with findings of studies conducted in Ibadan and Benin. [18],[19] Irinyenikan et al. found the mean age of women with gestational hypertension in Ibadan to be 30.4 ± 4.62 years, a figure similar but slightly higher than those of the participants in this study. [19] Similarly, Ebeigbe and Aziken found a slightly higher mean age among patients with gestational hypertension in Benin, South-South Nigeria. [18],[19]

The mean BMI (an important indicator of obesity) of the participants in Groups I and II were found to be 24.7 ± 5.0 kg/m 2 and 24.7 ± 5.4 kg/m 2 respectively. These findings were similar to those observed by Samy et al. in a group of Egyptian pregnant women. [20] However, the findings of this study were at variance with the findings of a similar study conducted among Ghanaian patients with gestational hypertension and their normotensive counterparts. [21] The observed differences could be as a result of differences in dietary and environmental factors that influence weight and height of the subjects recruited in the above two studies. There is, therefore, the need to conduct local studies to determine the prevalence, determinants and some of the complications of obesity and related entities in our local environment.

The mean gestational age of the study participants was found to be higher in the hypertensive group (33.3 ± 4.3 weeks) compared with their normotensive counterparts whose mean gestational age was 27.5 ± 6.8 weeks. However, the observed differences were not statistically significant (P = 1.4), thus the study participants were well matched in respect of their gestational age.

Primigravidae, who are women in their first pregnancies constitute about 47.3% of the participants in Group I compared to 38.75% of the Group II participants. This observation was similarly documented previously in some parts of Nigeria. [2],[3] Yakasai and Gaya reported that primigravidae constituted 81.4% of women affected by gestational hypertensive disorders including gestational hypertension. [2] Similarly, Ebeigbe and Aziken documented that majority of patients with hypertensive disorders were primigravidae. [19] Similarly, investigators in Ghana found that majority of patients with gestational hypertension were primigravidae. [21] This finding may be attributed to the long established fact that primiparity, grand multiparity as well as extremes of age are important risk factors for gestational hypertension, preeclampsia and eclampsia. There were no statistically significant differences in the prevalence of thyroid dysfunction in respect of parity and severity of gestational hypertension (P = 0.14).

Married women accounted for the majority of participants in the two groups studied. They constituted about 72.1% and 84.8% of the participants in Groups I and II respectively. There were slightly more single women in Group I compared to Group II participants. An analysis of the pattern of the occupation of the study participants showed that full-time housewives constituted about 40% and 39.2% of the participants in Groups I and II, respectively. This was an expected finding due to the relatively low literacy level of women in Nigeria, especially in the northern part where the study was conducted. There were also several literate women who were not allowed to work by their spouses due to cultural and perhaps some religious reasons.

The mean values of TSH in Groups I and II were 2.1 ± 1.7 mu/L and 1.6 ± 1.0 mu/L respectively. The difference observed was found to be statistically significant. This was similar to the findings of Gilbert et al. where a mean TSH of 0.02-2.15 was reported among normotensive Australian pregnant women. [22] However, Pasupathi et al. reported higher values among the similar group of Indian pregnant women. [23]

The different observations could be partly explained by the assay methods employed in the two studies. Enzyme micro particle immunoassay was employed in the Indian study while the more sensitive electrochemiluminescence immunoassay (ECLIA) was employed in the present study. ECLIA is generally more sensitive and specific than the enzyme micro particle immunoassay technique (EMIT). [24] EMIT usually employs polyclonal antibodies and may thus be more prone to positive interference by heterophilic antibodies, which may be found in the study participants. [25]

The mean fT 4 was found to be 15.3 ± 7.5 pmol/L and 19.0 ± 7.0 pmol/L in Groups I and II respectively. This finding was also at variance with the findings of Pasupathi et al. in India who reported a mean fT 4 that was almost twice the values found in this study. [23] This may also be attributed to the differences in the study participants and the assay methods used in both studies. The study conducted in India used EMIT technology to measure the serum levels of TSH, fT 4 and fT 3 while ECLIA, a more sensitive and specific technique was used in this study. [16],[23]

In addition, the mean serum fT 3 was 6.4 ± 2.7 pmol/L and 6.9 ± 2.6 pmol/L among participants in Group I and II respectively. However, there was no statistically significant difference between the mean fT 3 of the two groups. The observed values were also found to be lower than the values reported by Pasupathi et al. among Indian pregnant women. [23] Differences in the geographic locations and immunoassays used in the analysis may account for the disparity noted. However, similar values for fT 3 were reported by researchers in Australia among normotensive pregnant women who were mainly in their first trimester of pregnancy. [22]

The percentage prevalence of biochemical thyroid dysfunction was 23.6% and 10.3% among pregnant women in Group I and II respectively. A statistically significant difference was observed between the two groups. Sahu et al. reported 11.1% prevalence of thyroid dysfunction among Indian pregnant women. [26] This is also similar to the findings reported in this study. Similarly, workers in Iran reported a 14.6% prevalence of thyroid dysfunction from a study conducted on a cohort of 500 pregnant women. [27] The similarity observed could be due to the fact that both India and Iran are developing countries that share similar sociodemographic characteristics with Nigeria, where this study was conducted.

Studies have shown that hyperthyroidism (both sub-clinical and overt) are commonly encountered clinical disorders in pregnancy. [27] The prevalence of subclinical hyperthyroidism was found to be 1.2% and 1.6% among participants in Groups I and II respectively. This observation was similar to the findings reported by Casey et al., who demonstrated that 1.7% of the pregnant women in the United States of America had hyperthyroidism. They were also of the opinion that African-American women are more likely to have subclinical hyperthyroidism in pregnancy. [28] The similarities in the two results could partly be explained by the chemiluminescence immunoassay technique employed in both studies. The percentage prevalence of thyroid dysfunction found in this study was also similar to the findings of a similar work done on a cohort of Chinese pregnant women. Wang et al. analyzed the thyroid function profiles of 2,899 pregnant Chinese women and found thyroid dysfunction in 10.2% of the participants. [29] The Chinese study also found subclinical hypothyroidism as the commonest form of thyroid dysfunction. However, the percentage prevalence of thyroid dysfunction reported in this work was found to be at variance with the results reported among polish pregnant women. In Poland, Bańkowska et al . found a much higher percentage prevalence of 78.2% among women with gestational hypertension. [30] The high prevalence may be as a result of poor selection of participants. The authors stated that their study participants were all admitted into the wards, an action that might have affected the thyroid function and cause difficulty in interpreting the results, thereby resulting in the wrong conclusion. The control group, the analytical methods used to determine serum levels of TSH, fT 4 and fT 3 of the study participants, as well as the diagnostic criteria employed, were also not explicitly stated by the polish investigators.

Subclinical hypothyroidism was found to be the most common form of thyroid dysfunction in this study. Group I participants had a prevalence of 9.7% while Group II participants had a prevalence of 4.7%. These findings were similar to what was reported by workers in China, India, Iran and Nigeria. [11],[26],[27],[29] However, the findings were remarkably different from what was reported by workers who conducted a similar study in Poland. [30]

In the light of the high prevalence of thyroid dysfunction found in this study and what was reported in similar studies conducted elsewhere, the authors are of the opinion that all pregnant women should be screened for thyroid function abnormalities. The concept of universal screening where all pregnant women are routinely screened as opposed to aggressive case finding where only high risk pregnant women are screened for thyroid dysfunction is becoming popular in several countries. [20],[31],[32] The issue of universal screening of pregnant women is controversial. The proponents of universal screening believe that it is always better to err on the side of caution than expose women and their progeny to preventable complications. This is because of the availability of safe and effective treatment modalities as well as efficient laboratory monitoring for all forms of thyroid dysfunction. These are some of the reasons why universal screening is widely practiced in many developed countries especially in Europe, United States of America and Australia. [22],[33],[34] Similarly, the practice is becoming increasingly popular in many developing countries especially China and India. [26],[29] Some of the reasons that may be advanced for universal screening in Nigeria, especially in our locality include the availability of equipment and personnel that can perform both testing and interpretation of the thyroid function parameters. The issue of affordability is another important challenge that should be considered. However, many patients are now on some form of social insurance such as the National Health Insurance Scheme, which partly bear the cost of most laboratory investigations including thyroid function tests. [35]

However, there are also many investigators who favor aggressive case finding strategy for screening thyroid dysfunction and are thus opposed to the universal testing concept. This is the practice where only patients with the family or personal history of thyroid disorders, patients with any autoimmune disorder and patients with past history of neck irradiation are screened. Proponents of aggressive case finding believe that there are no sufficient reasons in the form of randomized control trials that evaluated the risk versus benefit of treating patients with laboratory diagnosis of subclinical thyroid dysfunction. Their stand was backed by many studies that consistently demonstrated that there were no statistically significant differences in the maternal and fetal outcome in euthyroid patients and those with various forms of subclinical thyroid abnormalities. [28],[31]

  Recommendations Top

Based on the findings from this study, the followings are hereby recommended:

  • Preconception clinics should be introduced in our hospitals aimed at screening women planning to conceive. Some of the biochemical investigations that may be performed include fasting blood glucose, total cholesterol, high density lipoprotein-cholesterol, low density lipoprotein-cholesterol, triglycerides, fT 3 , fT 4 and TSH.
  • All pregnant women should be encouraged to enroll for ante-natal care at an early gestational age. This will ensure early screening for medical disorders such as hypertension, diabetes, and various forms of thyroid dysfunction.
  • In view of the relatively high prevalence of thyroid dysfunction found in this study, all pregnant women should be screened for thyroid function abnormalities. If this is not possible due to issues related to availability or affordability of the screening tests, then women with gestational hypertension, those with family history of or a previous personal history of thyroid dysfunction, women who were rendered euthyroid or hypothyroid through the use of drugs or surgery, as well as those with past or current history of any autoimmune disorder should be preferably screened.
  • Reference intervals for all thyroid function test parameters should be developed. These should include those for pregnant women generally and trimester-specific reference intervals, in particular.
  • Clinicians especially Endocrinologists, Obstetric Medicine Specialists and Chemical Pathologists should be encouraged to conduct more studies, especially randomized controlled studies aimed at evaluating the benefit or otherwise of treating pregnant women with various forms of subclinical thyroid dysfunction.

Limitations of the study

The study was a descriptive cross-sectional study where the investigators had only one encounter with the study participants. Some of the participants that were found to be normotensive and euthyroid during the course of the study might have become hypertensive or developed some forms of thyroid dysfunction afterwards.

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