Thyroid Screening During Early Pregnancy and the Need for Trimester Specific Reference Ranges: A Cross-Sectional Study in Lahore, Pakistan

Abstract

BackgroundDerangements in thyroid hormone levels can cause multiple complications in the mother and the foetus. Thyroid stimulating hormone (TSH) and free thyroxine (free T4 or FT4) levels are used to screen for maternal thyroid dysfunction; these should be compared with population based trimester-specific reference ranges. Our goal was: to determine the prevalence of various thyroid derangements, in early pregnancy, according to the current reference ranges available; to determine the need for trimester specific reference ranges for the local population.MethodsA multi-centric, cross sectional population survey was conducted in Lahore, Pakistan. Serum TSH and FT4 levels were measured at the hormone lab of the Pathology department of Combined Military Hospital (CMH) Lahore. The results were entered and analysed using Statistical Package for the Social Sciences (SPSS) version 23. ResultsIn the 293 women sampled, mean FT4 and TSH levels were 15.03 (±5.62) pmol/L and 2.53 (±6.82) mIU/L respectively. According to the laboratory specific reference ranges, the prevalence of overt hyperthyroidism was 4.10%, (mean TSH= 0.03mIU/L); subclinical hyperthyroidism was 16.38%, (mean TSH= 0.17mIU/L); normal 70.65%, (mean TSH = 1.29mIU/L); subclinical hypothyroidism 4.44%, (mean TSH= 15.11mIU/L); overt hypothyroidism 4.44%, (mean TSH = 20.60mIU/L).ConclusionOur study showed a significant prevalence of thyroid dysfunction in the first trimester of pregnancy, and therefore highlights the need for more rigorous thyroid screening of women, in early pregnancy. There is a need to monitor these women in order to reduce maternal and foetal complications. Trimester specific reference ranges for thyroid hormones need to be developed in Pakistan.

Characterization of Fetal Thyroid Levels at Delivery among Appalachian Infants

“…Attempting to account for thyroid disorder in relation to socioeconomic class, Talat, et al did not show any association between income level and thyroid hormone levels [ 26 ]. However, they did note that most of the subjects in their study had free access to healthcare and regular checkups, which may have affected the results.…”

“…In another study, a Pakistani population’s prevalence of overt hypothyroidism was approximately 4%, while a study on northern Indian women showed a prevalence of 7%. The authors attributed differences in diet to partially account for this apparent disparity [ 26 , 27 ]. Furthermore, studies in China have shown variation in thyroid hormone levels in different races [ 28 ].…”

Trimester-Specific Reference Ranges for Thyroid Hormones of Pregnant Females at Tertiary Care Hospitals in Lahore, Pakistan

“…Assessment of thyroid status during pregnancy is of utmost importance for the initiation of treatment of newly diagnosed patients as well as for dose adjustment of patients already on hormone therapy. A decrease in the upper and lower limit of TSH has been noticed in pregnant females compared to the healthy nonpregnant population [13]. In clinical practice, measurement of free T4 and TSH, exceptionally the cut-off values for lower Free T4 and upper TSH reference limit provides the data for evaluating thyroid functioning in population.…”

“…The most common cause of maternal hypothyroidism in iodine-rich areas is Hashimoto's thyroiditis, whereas, in iodine-de cient areas like Pakistan, it is iodine de ciency [11]. A study conducted by Elahi et al in Lahore, Pakistan, revealed that around 79% of the pregnant females were iodine de cient, and 31% had goiter [12,13].…”

Thyroid Dysfunction: Risk and Management in Dentistry

“…Some of these functions are summarized in Table 1. (Khan et al, 2020) They assist in the growth, development and differentiation of all the body cells (Hofstee et al, 2019;Talat et al, 2019). They are a key regulator of the Basal Metabolic Rate (BMR) which is one of the major components of energy expenditure.…”