The thyroid gland in acromegaly: an ultrasonographic study

An association between acromegaly and goitre is well recognized. We have studied the incidence and morphology of goitre in acromegaly, and examined the role of IGF-I and TSH in goitre pathogenesis.

Thirty-seven subjects with acromegaly, active or in remission, were assessed by ultrasound to determine thyroid volume (TV) and morphology, and compared with normal controls. Nine subjects with acromegaly were also studied again following treatment with octreotide for 1 year.

Compared with controls, TV was greater (28.7 +/- 18.3 ml vs 5.4 +/- 2.6 ml, P < 0.001) and IGF-I levels were higher (62.0 +/- 34.8 nM vs 28.9 +/- 10.9 nM, P < 0.001) in subjects with acromegaly. Those with active disease tended to have larger glands (30.0 +/- 17.2 ml vs 22.2 +/- 16.7 ml, P = 0.18). The overall incidence of goitre was 92%. Twenty-seven subjects (73%) had nodules or heterogeneous thyroid echotexture. Subjects with nodular goitre had a longer duration of acromegaly than those with homogeneous glands (12.1 +/- 5.7 vs 7.6 +/- 4.0 years, P = 0.032). Those with nodular glands also had larger goitres than those with homogeneous glands (35.2 +/- 18.8 ml vs 19.5 +/- 11.9 ml, P = 0.032). Thyroid volume correlated with IGF-I levels (r2 = 0.38, P = 0.002) and body mass index (r2 = 0.24, P < 0.001), and there was an inverse relationship with TSH levels (r2 = 0.46, P = 0.032). Patients studied again after treatment with octreotide for 1 year had a reduction in TV from 32.6 +/- 16.1 to 27.6 +/- 17.0 ml (P = 0.041).

This study confirms that goitre is a common finding in acromegaly. Our findings suggest that early in the course of the disease, diffuse goitre occurs. Subsequently, thyroid autonomy and nodule formation develop, and further growth may occur independent of TSH. With control of GH hypersecretion, a reduction in thyroid size occurs, but this may be limited by the extent of thyroid nodularity.