Thyroid Profile of Term Appropriate for Gestational Age Neonates in Nigeria: A Forerunner to Screening for Congenital Hypothyroidism

Abstract

Thyroid hormones in normal quantity are vital for physical growth and mental development during fetal and postnatal life. The available publications in Sub-Saharan Africa on the thyroid function of newborn infants was reported in babies delivered in moderate to severe goitre zones; utilizing the hormone levels from these studies may have a measure of bias. Newborn screening for congenital hypothyroidism (CH) in Sub-Saharan Africa is still a mirage, the technicality of the best timing for collection of blood samples need to be studied. Consequently, we report the serum levels of total thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) at birth and at 72 h after birth, and to ascertain if there is any significant difference between them. This was a prospective cross-sectional study (6 months period) between November and April 2005. One hundred and fourteen apparently healthy term AGA neonates had their thyroid function analyzed, the females (59) were slightly more in number than the (males 55). Most of them were between GA of 37-38 weeks at birth. The observed 72 h mean values of serum T3 and T4 (1.06 and 101.38 nmol l(-1)) compared with the cord values at birth (0.89 and 75.48 nmol l(-1)), was not statistically significant. The mean cord TSH levels (13.59 mU l(-1)) compared with 72 h serum TSH levels (10.25 mU l(-1)) was also insignificant p = 0.3. For Sub-Saharan Africa cord TSH analysis may be a reasonable choice for newborn screening for congenital hypothyroidism.

Thyroid function profile in cord blood and postnatal changes at 24 and 72hours in healthy term Nigerian neonates

“…This may result in more severe reduction in the iodine content in the newborn thyroid and consequently reduction in its functional capacities. The demonstrated pattern of postnatal changes at 72hours in this study (higher mean T 3 , T 4 and lower TSH) compared with mean cord blood levels is similar to that reported in Benin 15 . This suggest that the postnatal changes in neonatal thyroid function are qualitatively the same irrespective of geographical location but there may be slight quantitative differences.…”

“…Coincidentally a similar method of assay was used (ELISA technique), though the test kits were different. The Benin study 15 showed lower mean serum T 4 and higher mean serum T 3 and TSH than this present study. This observation may be due to the differences in location, Sokoto being a mild goiter zone while Benin is in an area of moderate goiter.…”

“…In the same study done in Benin, 15 the researchers found no significant differences between the mean cord blood T 3 , T 4 , and TSH and the mean serum values of these hormones at 72hours (p=0.36, 0.08, 0.33 respectively), meaning that it makes no difference whether screening for congenital hypothyroidism is done with cord blood or venous blood at 72hours, consequently the same reference values may be utilized. This is however, contrary to this present study which demonstrated differences between the cord blood and 72hours mean concentrations of T 3 and TSH (p=0.05, 0.001 respectively).…”

“…Lastly, quantity of TSH in the cord is not affected by maternal levels as compared to T 4 levels because TSH does not cross the placenta because of its high molecular weight 9,10,11. Thyroid profiles have been described in neonates in North America and Europe 12,13 with the establishment of reference values which are utilized by neonatal screening centers 12,13 . However, in Africa, limited studies have been documented 14,15 . It was, therefore, considered that since no study has been done describing thyroid profile in term neonates in Sokoto, and little is known about its postnatal changes in Nigerian neonates, particularly in this part of the country, it was pertinent to undertake this study.…”

Screening for congenital hypothyroidism: results of screening 5600 Ardabil province infants

“…[12][13][14][15][16] According to research in the world, the prevalence of congenital hypothyroidism varied from 0.14 per 1,000 live births in Japan to 14.7 per 1,000 infants in Nigeria which lower than the present study. 7,17,18 The causes of the different prevalence of the disease in different parts of the world can be due to the different contraceptive criteria for the diagnosis of hypothyroidism, use of T4 or TSH to screen, iodine deficiency in some parts of the world, the percentage of different marriages and ethnic and racial differences. [19][20][21][22][23][24][25] In this study, the rate of recall was 5600 cases or 35 cases per 1000 (3.5%) infants.…”