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Application of the captopril test to patients identified as abnormal by screening confirms all cases of primary hyperaldosteronism but false positive or equivocal results, necessitating further investigation, may occur in some patients with essential hypertension.

To compare the effect of three treatments for thyrotoxicosis on subsequent body weight, a retrospective survey of 65 patients was performed. The effect of thyroxine replacement on body weight in 25 patients with primary hypothyroidism was also examined. In one year after starting therapy 21 patients treated with carbimazole gained a mean of 5.4kg (95% confidence interval 3.6 to 7.2kg); 20 patients after thyroidectomy gained a mean of 6.3kg (95% c.i. 3.4 to 9.2kg); and 24 patients given radioiodine gained a mean of 7.4kg (95% c.i. 5.2 to 9.6kg), p less than 0.001 in all three groups. The weight gain in the three groups was not significantly different. 54-67% of the weight gain occurred in the first three months. The patients treated for hypothyroidism had lost an insignificant amount of weight 12 months after starting therapy--mean change was -0.6kg (95% c.i. -2.2 to +1.1kg) p greater than 0.1. This data suggests that all patients treated for thyrotoxicosis will gain body weight irrespective of the treatment used, but patients treated for primary hypothyroidism will not lose an appreciable amount of weight. Therefore dietary advice should be given, where appropriate, at the onset of any treatment of thyroid dysfunction.

A radioimmunoassay for luteinizing hormone-releasing hormone (LH-RH) has been developed. Antisera were raised against the decapeptide conjugated to albumin in rabbits and against the 3-10 octapeptide conjugated to albumin in rats. LH-RH was iodinated with 125I and purified on Sephadex, the most immunoreactive fractions of the 125I-LH-RH being eluted after 125I. A serum assay was developed using a simple methanol extraction procedure. The rabbit antiserum could detect levels of LH-RH in the jugular vein of the sheep at various times and in the rat on the afternoon of pro-oestrus. The assay using the rat antiserum was 30 times more sensitive and could detect LH-RH in peripheral serum in man. 10-20 pg/ml in peripheral serum of man, but the RIA could be used to measure the disappearance and clearance of LH-RH after intravenous injection of large test doses (Jeffcoate et al. 1974a). In this study we describe the details of a RIA of LH-RH in serum from man, sheep and rat.

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