Hot nodules of the thyroid.
Hot nodules of the thyroid are rare as compared to other disorders of that gland. They can be further subdivided into (a) T.S.H. dependant (b) euthyroid autonomously functioning thyroid lesions (A.F.T.Ls.) with partial or total suppression of the extranodular thyroid tissue (c) toxic A.F.T.Ls. We report here a study of 27 hot nodules studied at Thyroid Clinic of Topiwala National Medical College between 1973 and 1976.
All the patients attending the thyroid clinic had a detailed clinical examination and a standard I131 uptake test. Thyroid scan was done in all those who had a palpable nodule. T3-charcoal uptake estimation and thyroxine suppression test were done in some. The latter test was done by recording a scan before and after giving the patient 1-thyroxine sodium 0.3 mgm daily for six weeks. Suppression was not tried in clinically toxic patients. The diagnosis of hot nodules was based on the presence of a clinically palpable nodule which on scan was seen to take up more I131 than the rest of the gland.
Twenty seven patients with hot nodules and 118 patients with cold nodules were seen during the period of study, thus giving a ratio of 1:4.3. Amongst the patients with hot nodules there were 4 males and 23 females, giving a ratio of 1:5.8. The age distribution has been shown in Table 1.
The youngest patient was only 4 years old.
Of the 27 patients, 17 were euthyroid and 10 were toxic. All the 10 toxic patients were women. Of these 4 had clinically toxic state and in six the diagnosis was suggested by the laboratory tests only.
The mean age of the euthyroid patients was 38.6 years with a S.D. of 11.8. The mean age of the toxic patients was 45.5 years with a S.D. of 15.25. Thus, the toxic group was one decade older than the euthyroid group., 
The duration of the nodule varied from 1 month to 15 years. Seven patients were not sure of the duration of the nodule. The four clinically toxic patients had the nodule for 4-15 years and had noticed the symptoms of toxicity only recently.
The area of the nodules as measured on the scan varied from 0.66 sq.cm. to 3.76 sq.cm. The mean nodular size in the euthyroid patients was 1.9 sq.cm. with a S.D. of 0.905. In the toxic patients it was 1.77 sq.cm. with S.D. of 0.52. Hence there was no difference in the sizes of the two types of nodules.
Of the 9 patients who had a T4 suppression test, 3 showed complete suppression of the nodule. In them, on clinical examination, the nodules had almost disappeared. A repeat scan was possible in only one of them as the I131 uptakes had fallen to less than 1% in the other two. In the third patient in whom the repeat scan was done, the nodule was not seen on the scan and the normal gland had taken up I131. None of the patients developed signs of toxicity during the test.
Only one patient who was toxic had involvement of the eyes. She complained of proptosis, burning and watering of eyes. On examination, she had exophthalmos, inability to wrinkle the forehead or converge the eyes. The movements of the eyes were restricted in all the directions.
Two of the toxic patients had developed auricular fibrillation. Both of them were put on digoxin and propranolol. They reverted back to sinus rhythm. Both patients were above 60 years of age.
Seven of the 10 toxic patients have been treated. Three of them were above the age of 40 and hence were treated with I131. One patient returned to a normal state within 9 months. A repeat scan showed absence of the nodule and normal I131 concentration in rest of the gland. One patient needed a second dose. The third patient did not return for follow-up.
Hemithyroidectomy was done on 3 patients. On histopathological examination the lesions were diagnosed as follicular adenoma in all the three. None developed complications or recurrence after surgery.
Carbimazole was administered to 2 patients. Both showed improvement. One of them opted for surgery at a later date. The other patient was the one with eye signs as well as auricular fibrillation. The fibrillation reverted to sinus rhythm, but the eye signs did not change. The other symptoms of toxicity, I131 uptake and PBI131 returned to normal. However, the scan still showed the presence of the hot nodule.
Nine of the euthyroid patients have been followed for varying periods upto three years. None of the nodules progressed to toxicity or showed increase in size. On repeat scans none of the nodules showed areas of degeneration.
The male to female ratio varies amongst the different studies on hot nodules, but some authors ,  have reported a preponderance of females as in the present series.
The youngest patient was only four years old and it was interesting to find a T.S.H. dependant hot nodule and not just a remnant of a gland. The mean age of the toxic patients was a decade more than the euthyroid patients. Toxicity is known to be commoner amongst older patients of A.F.T.Ls,
The ratio of euthyroid A.F.T.Ls. as compared to toxic ones varies in various studies Table 2.
Four patients who were clinically toxic had been aware of the presence of nodules for a period of 4 to 15 years; however, they had experienced the symptoms of toxicity only recently. This may be taken as an indication of recent increase in the function of the nodule.
In the present study, there was no difference in the mean area of euthyroid and toxic nodules. Other workers,, , ,  on the other, hand have reported that the size of the euthyroid A.F.T.Ls. was smaller than the toxic ones. Hence they presume that the smaller nodules produce less hormone than the bigger ones and that the smaller nodules may be precursors of bigger toxic ones. However, all these workers have measured the mean diameter and not the area.
The thyroxine suppression test helped us to diagnose and treat three patients of T.S.H. dependant hot nodules with total disappearance of the nodule.
Molnar et al6 have noted that clinical features of toxicity and laboratory investigations do not always go hand in hand amongst patients of toxic A.F.T.Ls. In this series also, only four patients had clinical features suggestive of toxicity. One patient of toxic A.F.T.L. had eye signs. Other authors have not found involvement of the eyes in their patients of A.F.T.Ls.. , ,  Two of the patients with toxic A.F.T.Ls. had auricular fibrillation and as expected6 both were more than 50 years old.
Three toxic patients with A.F.T.Ls. were treated with I131. The number is too small for any conclusions but we can only state that all toxic nodules do not require very large doses of I131 as suggested by others., , ,  We found surgery as a quick and effective method of treating toxic A.F.T.Ls. Carbimazole was found to be effective in two patients with toxic A.F.T.Ls. Surprisingly, the repeat scans showed less I131 uptake in the nodule as compared to the rest of the gland.
Unlike what is stated in the literature.,  none of the patients who have been followed up for varying periods upto three years have shown areas of degeneration or progression to toxicity.
We are thankful to the Dean, Topiwala National Medical College for allowing us to carry out this study.