ABSTRACT
The short ACTH stimulation test, using 250 micro g synthetic adrenocorticotropic hormone [ACTH], has been advocated as a safe alternative procedure to the dangerous insulin stress test, for assessment of the function of the hypothalamic-pituitary-adrenal [HPA] axis. However, it has been suggested that a maximal cortisol response can be achieved with a much lower ACTH dose, hinting at the possibility that reducing the dose might further enhance the sensitivity of the procedure. Aim of work: The aim of this study was to assess the potential role of the low dose ACTFI challenge in the evaluation of the HPA axis function, compared to the standard 250.micro g ACTH test in normal adults. Subjects and The study was conducted on 21 apparently healthy Egyptian adult volunteers, who underwent stimulation with three different doses [1 micro g, 5 micro g and 250 micro g] of synthetic ACTH [1-24]. Blood samples were obtained at 0, 15, 30 and 60mm for measurement of serum cortisol concentration and 0. 60min serum samples were also used to measure adrenal precursors Delta-4-androstendione [delta-4A], Dehydroepiandrosterone [DHEA] and 17- hydroxyprogesterone [17 OHP] levels, to investigate the efficiency of the low doses of ACTH for detection of late-onset congenital adrenal hyperplasia [LOCAH]. The study revealed no significant difference between mean cortisol level at 15, 30 and 60min in response to the three different doses. Using the 1 or 5 micro g doses, all subjects [100%] reached adequate cortisol response at 30min, while using 250 micro g dose, 90% of subjects reached adequate cortisol response at 60min. The steroid precursors showed no significant difference at 60min in response to the three doses. During the study, 4 cases, two males and two females, were accidentally found to have elevated steroid precursors in response to ACTH. These cases were found to have 21- hydroxylase deficiency, as evidenced by the elevated levels of stimulated 17 OHP, thus, were diagnosed as LOCAH. The low doses [1micro g and 5 micro g] ACTH test responses were found almost comparable to the 250 micro g doses on normal subjects, and can be used to induce adequate adrenal stimulation. They were also useful in detecting latent cases of congenital adrenal hyperplasia