A. Gunn

Re-evaluation of the captopril test for the diagnosis of primary hyperaldosteronism

OBJECTIVE We aimed to re‐evaluate the captopril test in the diagnosis of primary hyperaldosteronism.

Beta‐adrenoceptor blockade and anaesthesia for thyroidectomy

The administration of beta‐adrenoceptor blocking drugs in the pre‐operative preparation and operative management of thyrotoxic patients undergoing subtotal thyroidectomy is reviewed. Particular reference is made to some of the recent advances and it is emphasised that there has been a considerable reduction in the incidence of problems following judicious use of these drugs. The choice of anaesthetic technique employed for thyroidectomy is less important than the degree of control of thyrotoxicosis by the beta‐adrenoceptor blocking drug. Propranolol has proved safe and effective for the majority of patients. The longer acting agent nadolol is easier to administer, particularly in the peri‐operative period. Patients are rendered less thyrotoxic and safety thereby enhanced by adding potassium iodide for 10 days pre‐operatively. The combination of nadolol and potassium iodide offers real advantages in the preparation of the thyrotoxic patient for surgery.

Autoantibodies in thyrotoxicosis: a quantitative study of their behavior in relation to the course and outcome of treatment

Many previous investigations have looked into the association between thyroid autoantibodies and the course of thyrotoxicosis. However, the interpretation of these studies is often difficult, owing to their largely retrospective nature, and comparability is limited because of differences in criteria and sampling schedules. The purpose of this study was to investigate prospectively the serial changes in autoantibodies under carefully controlled conditions during treatment of thyrotoxicosis, and to relate these changes to clinical outcome and surgical histology. Sixty-seven patients with Graves’ disease were studied for 24 months; 34 were treated medically and 33 surgically. Anti-thyroglobulin (anti-Tg) and anti-microsomal (anti-M) antibodies were measured on 16 occasions. The frequency of patients showing anti-Tg fell progressively irrespective of the type of treatment, while that showing anti-M fell initially but rose again. Weak associations were found between anti-Tg and suppressibility after 5 months of drug treatment, between the cumulative amount of anti-M and the final TSH levels in those who remained euthyroid after drugs, and between the circulating levels of anti-M just before surgery and the frequency of clinical hypothyroidism 18 months later. However, no significant correlation emerged between the cumulative amount of antibody during the two-year period and the final TSH level or clinical result after surgery, nor between the prevailing antibody level and surgical histology. Wide, rapid and apparently random fluctuations of antibody levels in individuals cast considerable doubt upon the value of single estimations in the distinction of antibody-positive from antibody-negative members of a thyrotoxic population. We conclude that the measurement of thyroid autoantibodies in Graves’ disease has little practical value for the clinician.

ALTERED ENDOCRINE RESPONSE TO PARTIAL THYROIDECTOMY IN PROPRANOLOL‐PREPARED HYPERTHYROID PATIENTS

The endocrine response to partial thyroidectomy in a group of twenty hyperthyroid patients prepared with propranolol alone was compared to that of a matched control group of ten euthyroid patients. In propranolol‐prepared patients the glucose response to surgery was reduced (P< 0·05) for up to 4 h post‐operatively and biochemical hypoglycaemia was noted in one patient. Both thyroxine and triiodothyronine (T3) fell significantly, associated with a marked rise in reverse T3. Growth hormone levels were higher (P<0·05) both pre‐and post‐operatively in propranolol‐prepared patients, whereas prolactin levels, although similar pre‐operatively, were lower (P<0·05) in these patients post‐operatively. Cortisol and ACTH levels were lower (P < 0·05) both before and following thyroidectomy in propranolol‐prepared patients. These results suggest that the endocrine response to surgical stress is markedly altered in propranolol‐prepared hyperthyroid patients.

Time, carbimazole and the outcome of Graves’ disease

A detailed comparison was made over 18 months of the serial mean 20 min132 I uptake behavior between 15 Graves’ disease patients whose hyperthyroidism ultimately remitted (Group E) and 20 in whom it persisted (Group R). All were treated with carbimazole and T3. There were no qualitative differences in uptake between the 2 groups. In both, the uptake fell with time, and the slopes were parallel. The fact that the mean uptake started lower in Group E patients was sufficient to explain why it became normal much earlier than that of Group R, which had not normalized by 18 months. In both groups, over half the overall fall in uptake occurred during the first month of treatment with carbimazole. We conclude that, while time remains the most important determinant of outcome in Graves’ disease, some possible immunosuppressive action of carbimazole can shorten the cycle length to a major degree.

THE VARIATION IN SERUM TRIIODOTHYRONINE (T3) ACHIEVED DURING SUPPRESSION TESTING IN THYROTOXICOSIS

Regular measurement of thyroidal radioiodine uptake has been widely used as a means of monitoring continued extrapituitary stimulation of the thyroid during the treatment of thyrotoxicosis with carbimazole and triiodothyronine (T3). However, it is unclear to what extent the serum T3 level may vary at the time of testing, nor what effect this might have on the uptake of radioiodine. Two studies have been undertaken. In the first, serum T3 levels in twenty‐four thyrotoxic patients were measured at intervals during an 18‐month course of carbimazole combined with T3, 20 μg qid. Considerable variations in the highest and lowest levels of serum T3 were found both between and within individuals. The second study was on twenty‐three thyrotoxic patients thought to be entering remission because the iodine uptake after 5 months of drug treatment had fallen to less than 50% of the pretreatment value (suppressors). The changes in uptake of radioiodine after 5 and then 6 months of treatment were compared in seven patients, who received carbimazole and T3 throughout, with the corresponding changes in the remaining sixteen patients, whose T3 alone was withdrawn prior to the uptake test at month 6. The mean degree of suppression remained unchanged by month 6 in the first group. In the second group, however, the mean uptake rose significantly, and nine of the sixteen patients would have been classified as non‐suppressors at the sixth month (i.e. uptake greater than 50% the pretreatment value) had their failure to maintain high serum levels of T3 gone undetected. The first study indicated this could well happen in routine circumstances, and it is suggested that the reliability of suppression tests be checked with simultaneous measurement of serum T3.