Nico J. Smits

DETERMINANTS OF THYROID VOLUME AS MEASURED BY ULTRASONOGRAPHY IN HEALTHY ADULTS IN A NON‐IODINE DEFICIENT AREA

Thyroid volume was measured by ultrasonography in 50 healthy adults (25 males, 25 females, age 20‐70 years) living in the non‐iodine deficient area of Amsterdam. Thyroid volume was 10‐7 ± 4–6 ml (mean ± SD, range 2.7‐20.4 ml). No relation was found between thyroid volume and any of the following parameters: plasma TSH, T4, T3, thyroglobulin (Tg), urinary iodine excretion, tobacco and alcohol consumption. Thyroid volume in males (12.7 ± 4.4 ml) was greater than in females (8.7 ± 3.9 ml, p = 0.0014), but no sex difference was observed in the ratio of thyroid volume to body weight (males, 0.16 ± 005 ml/ kg; females 013 ± 0.06 ml/kg; NS). Thyroid volume was positively related to body weight, but not to age. We conclude that the sex difference in thyroid volume is due to the difference in body weight between males and females. Lean body mass is presumably the most important physiological determinant of thyroid size in subjects living in a non‐iodine deficient area.

Comparison of placebo with L-thyroxine alone or with carbimazole for treatment of sporadic non-toxic goitre

The efficacy of treatment with TSH-suppressive doses of L-thyroxine (T4, 2.5 micrograms/kg body weight daily) either alone or combined with carbimazole (CBZ, 40 mg daily) was studied in 78 patients with sporadic non-toxic goitre in a prospective placebo-controlled double-blind randomised clinical trial. Treatment was given for 9 months, with 9 months of follow-up. A response to treatment as measured by ultrasonography was found in 58% of the T4 group, in 35% of the T4/CBZ group, and in 5% of the placebo group. The mean (SEM) decrease of thyroid volume at 9 months in the responders was 25% (2). After discontinuation of treatment, thyroid volume increased in the responders and had returned to base-line values after 9 months of follow-up. In the placebo group mean thyroid volume had increased by 6% (4) at 4 months, 20% (7) at 9 months, and 27% (8) at 18 months. The findings show that untreated sporadic non-toxic goitre continues to increase in size; T4 is effective in the treatment of the disorder; and the addition of CBZ has no therapeutic advantage.

Interrelationships between age, thyroid volume, thyroid nodularity, and thyroid function in patients with sporadic nontoxic goiter

PURPOSEnTo test the hypothesis that during the natural history of sporadic nontoxic goiter (SNG), a diffuse goiter precedes a multinodular goiter with gradual development of autonomous thyroid function.nnnPATIENTS AND METHODSnA cross-sectional survey of 102 consecutive patients with SNG (seven male, 95 female) was performed. Thyroid volume was measured by ultrasonography, and plasma thyroid-stimulating hormone (TSH) by a sensitive assay (TSH immunoradiometric assay).nnnRESULTSnPatients with a multinodular goiter were older and had a larger thyroid volume than patients with a diffuse or uninodular goiter. Plasma free thyroxine (T4) and total triiodothyronine (T3) were higher and plasma TSH was lower in patients than in normal subjects. Free T4 was higher in the subgroup of patients with a multinodular goiter and a decreased TSH response to thyrotropin-releasing hormone. Plasma TSH (y, in mU/L) was negatively related to thyroid volume (x, in mL): y = 8.2x-0.667 (r = 0.578, p less than 0.001). Thyroid volume (y, in mL) was positively related to age (x, in years): y = -21.8 + 2.0x (r = 0.455, p less than 0.001); and to duration of goiter (x, in years): y = 40.6 + 2.1x (r = 0.505, p less than 0.001). The annual increase in thyroid volume was calculated at 4.5%.nnnCONCLUSIONnThe data suggest a continuous growth of SNG and provide support for the concept of increasing thyroid nodularity and autonomy of thyroid function--related to increasing thyroid volume--during the natural history of this disorder.

Thyroid function and thyroid size in normal pregnant women living in an iodine replete area

OBJECTIVE The interpretation of the changes in thyroid hormone concentrations during normal pregnancy is a matter of debate involving, in some geographical regions, enhanced thyrold activity in early pregnancy and a hypothyroid state In the third trimester.

Lean body mass as a determinant of thyroid size.

Males have a larger thyroid gland than females, and this has been related to the difference in body weight. In view of the different body composition of men and women, we hypothesized that lean body mass is a better determinant of thyroid volume than body weight.

THE VALUE OF THYROID VOLUME MEASURED BY ULTRASONOGRAPHY IN THE DIAGNOSIS OF GOITRE

Thyroid volume was measured by ultrasonography in 80 euthyroid patients with sporadic nontoxic goitre and in 50 healthy adults, all residing in non‐iodine deficient areas. All patients were referred because of complaints of goitre and had been diagnosed as cases of goitre by inspection and palpation. The thyroid volume in 15 patients with goitre (19%) was within the normal reference range (4.9–19.1 ml). Fourteen of the 15 patients had thyroid nodules larger (mean diameter 2.9 ± 1.1 cm) than those detected in nine of the healthy adults (mean diameter 0.8 ± 0.6 cm; P < 0.001). Thyroid size as estimated by inspection and palpation (grade OA to III according to Stanbury et al, 1974) was poorly related to thyroid volume measured by ultrasonography. In conclusion: (1) a thyroid volume within the normal reference range does not rule out the presence of nodular goitre; and (2) application of thyroid volume measurement by ultrasonography may prevent overestimation of goitre prevalence in epidemiological surveys.

THE LONG‐TERM OUTCOME OF THYROIDECTOMY FOR SPORADIC NON‐TOXIC GOITRE

To study the long‐term outcome after thyroidectomy, 113 sporadic non‐toxic goitre patients who underwent thyroidectomy in our hospital in the period 1974–1983, were studied. Five patients complained of recurrent goitre; a goitre was found on inspection and palpation in these five and in 15 others. There were no differences between the 20 patients with goitre and the 93 patients without goitre with regard to sex, age, duration of goitre, indication and type of thyroidectomy, postoperative thyroid hormone medication, period of follow‐up, and T4, T3, or TSH plasma values at the time of follow‐up examination. Twenty‐three patients complained of voice changes since thyroidectomy. In a case control study, included in this follow‐up study, 19 patients with goitre, i.e. thyroid size I and II as estimated by inspection and palpation (cases), and 16 patients without goitre, i.e. thyroid size OA and OB (controls), were studied in more detail. No difference between cases and controls was found in any of the above mentioned parameters that could explain the recurrence of goitre. Thyroid volume (median) was greater in the cases (34–1 ml, range 7.9–83.4) than in the controls (10.3 ml, range 2.5–48.7) (P < 0.001), although a considerable overlap between the two groups was observed. One or more thyroid nodules were found in 89.5% of the cases and in 62–5% of the controls (NS). Serum thyroid growth stimulating immunoglobulin (TGI) was present both in cases (68%) and controls (50%). TGI was present in high titres in all five patients who complained about recurrent goitre. Thyroid volume was negatively related to the plasma level of TSH (r =−0.36, P < 0.05), and positively but not significant to serum TGI. In conclusion: (1) a goitre is found in 17.7% of sporadic non‐toxic patients at long‐term follow‐up after thyroidectomy, not related to age, sex, duration of goitre, indication or type of operation, postoperative thyroid hormone medication, period of follow‐up, or plasma T3, T4, or TSH; (2) TGI is more prevalent in patients who complain of recurrent goitre after thyroidectomy; (3) thyroidal nodular disease persists in the majority of patients after thyroidectomy.

Ultrasonographic versus scintigraphic measurement of thyroid volume in patients referred for 131I therapy.

The activity of 131I to be administered as therapy to patients with thyroid disease is usually calculated from 24 h radioiodine uptake and thyroid volume. The aim of the present study was to compare thyroid volume, measured by scintigraphy and ultrasonography, to evaluate the impact of these methods on the calculated 131I dose. Forty patients (20 with diffuse toxic goiter and 20 with multinodular toxic or nontoxic goiter) were investigated. On the same day, thyroid volume was measured by ultrasonography (using transverse scans at 5 mm intervals) and by scintigraphy, using either the ellipsoid formula (SC-E: [symbol: see text]/6 x height x width x depth) or the Himanka formula (SC-H: 0.33 x (planimetric surface in pixels)3/2). With ultrasonography, the size of diffuse goiters was smaller than that of nodular goiters (median values and range: 18 ml (11-46) and 50 ml (14-198) respectively, P < 0.001). Both scintigraphic methods, however, failed to demonstrate a significant difference between diffuse and nodular goiter size. In patients with diffuse goiter, thyroid volume measured by SC-E did not differ from that measured by ultrasonography, whereas thyroid size was overestimated by 53% using the Himanka formula. In contrast, in patients with nodular goiter, thyroid volume measured by SC-H did not differ from that measured by ultrasonography, whereas the ellipsoid formula underestimated thyroid size by 48%. The overestimation of diffuse goiter size by the Himanka formula resulted in a relatively modest median excess of 96 MBq (range -118 to +248 MBq) of the calculated 131I dose. The underestimation of nodular goiter size by the ellipsoid formula resulted in a calculated dose that was 278 MBq lower (range -1624 to +141 MBq). The median calculated 131I dose based on the Himanka formula was not different from that based on ultrasound, but large differences in calculated 131I dose (up to 1280 MBq) were found in individual cases. In conclusion, thyroid volume can be assessed with accuracy by scintigraphy using the ellipsoid formula in patients with diffuse goiter. Wide differences, however, are observed in the size of nodular goiters measured by scintigraphy and ultrasonography.