Congenital Hypotyroidism (CH) T4

The NEONATAL TOTAL-T4 Screening ELISA is a competitive ELISA in which both T4 contained in the blood specimen (free T4 and TBG-bound T4) and a labelled-T4 competitively bind to the anti-T4 antibodies covering the microplate. The labelled-T4 is measured through the reduction of 3,3’-5,5’-tetramethylbenzidine (TMB) by the HRP. The intensity of this signal is therefore inversely proportional to the concentration of T4 present in the sample.

Congenital adrenal hyperplasia (CAH) refers to a group of disorders resulting from defective steroidogenesis. There are several types of congenital adrenal hyperplasia described: deficiency of 21-Hydroxylase, 17-α-Hydroxylase, 3-β-Hydroxysteroid Dehydrogenase, 11-β-Hydroxylase, or Cytochrome P450 Oxidoreductase and finally congenital lipoid adrenal hyperplasia.

In more than 90-95% of cases, CAH is caused by a deficiency in enzyme 21-Hydroxylase, which controls the production of cortisol and aldosterone in the adrenal gland. This 21-Hydroxylase deficiency is subdivided into two subcategories:

Classic congenital adrenal hyperplasia, which itself can be categorized as salt loss and simple virilizing forms. Classic CAH is the most serious form and can lead to adrenal crisis and premature death if not managed quickly.

The most common symptoms of classical CAH are hypertrophic adrenal glands producing excessive quantities of androgens, with aldosterone deficiency. The result is excessive salt loss from birth, leading to hyponatremia, dehydration, hypovolemia and hypotension, which endangers the patient’s survival. In girls, sexual ambiguity with varying degrees of virilization is usually present. 

In infants, the determination of 17-hydroxyprogesterone (17-OHP) levels can identify classic forms of 21-Hydroxylase deficiency. Because premature babies typically have higher 17-OHP concentrations, the cut-off is often weighted by gestational age at birth and/or newborn weight.