A distribution method for analysing the baseline of pulsatile endocrine signals as exemplified by 24-hour growth hormone profiles

OBJECTIVE: To develop a method for quantifying the distribution of concentrations present in hormone profiles, which would allow an observer-unbiased estimate of the time concentration attribute and to make an assessment of the baseline. DESIGN: The log-transformed concentrations (regardless of their temporal attribute) are sorted and allocated to class intervals. The number of observations in each interval are then determined and expressed as a percentage of the total number of samples drawn in the study period. The data may be displayed as a frequency distribution or as a cumulative distribution. Cumulative distributions may be plotted as sigmoidal ogives or can be transformed into discrete probabilities (linear probits), which are then linear, and amenable to regression analysis. Probability analysis gives estimates of the mean (the value below which 50% of the observed concentrations lie, which we term 'OC50'). 'Baseline' can be defined in terms of percentage occupancy--the 'Observed Concentration for 5%' (which we term 'OC5') which is the threshold at or below which the hormone concentrations are measured 5% of the time. PATIENTS: We report the use of applying this method to 24-hour growth hormone (GH) profiles from 63 children, 26 adults and one giant. RESULTS: We demonstrate that GH effects (growth or gigantism) in these groups are more related to the baseline OC5 concentration than peak concentration (OC5 +/- 95% confidence limits: adults 0.05 +/- 0.04, peak-height-velocity pubertal 0.39 +/- 0.22, giant 8.9 mU/l). CONCLUSIONS: Pulsatile hormone profiles can be analysed using this method in order to assess baseline and other concentration domains.     

Marfan syndrome affecting four generations of a family without ocular involvement

Thirty eight relatives of a patient with Marfan syndrome were screened for the presence of this disorder. Marfan syndrome was newly diagnosed in living members of 4 generations in this family without evidence of ocular abnormality in any. After screening, 10 relatives were newly diagnosed as having definite, and 5 relatives as having possible, Marfan syndrome. Family screening has drawbacks as well as benefits for the patients. The main benefit is the identification and treatment of previously undiagnosed patients at risk of cardiac complications which are the major cause of mortality. The drawbacks include employment problems created for patients with Marfan syndrome as a direct consequence of our screening programme and the anxiety induced in previously asymptomatic family members who did not realize that they could be at risk. Also, the 4 adult patients with possible Marfan syndrome found it difficult to accept that a definite diagnosis could not be reached after they had been invited to attend a screening programme for a serious genetic disorder. This report illustrates the importance of screening all the relatives of a patient with Marfan syndrome to identify previously undiagnosed cases. However, before screening a family, the physician should be aware that a clear diagnosis may not be reached in all patients, and financial, psychological or social problems may arise as a result of the screening programme.     

Gated cardiac magnetic resonance structural imaging: optimization by electronic axial rotation

Most magnetic resonance imaging has used body orthogonal axes with the Z axis placed along the length of the body and the X and Y axes at right angles to the body. This orientation is not optimum for the heart; visualization of sections along the short and long cardiac axes would best define cardiac structural detail and functional status. The new orientation was accomplished by selection of electronic angulation of the magnetic fields for each subject rather than by attempting to approximate the cardiac axes by altering the position of the patient. This technique improved visualization of comparative wall segments, valvular structures, and the true four-chamber view of the heart, and also gave the best visualization of the pericardium. In addition, more accurate estimates of chamber size and myocardial mass can be made from the short-axis orientation, since the sections are orthogonal to the myocardium.