Increased Incidence of Euthyroid and Hyperthyroid Goiters Independently of Thyrotropin in Patients with Acromegaly

Abstract

The incidence of palpable goiters, the thyroid functional state and thyroid radioisotope uptake was analyzed retrospectively in 80 patients with acromegaly and 80 patients with prolactinomas. 71% of all patients with acromegaly had an enlargement of the thyroid (goiter); 49% of them had diffuse and 39% nodular goiters. The incidence of goiters in patients with prolactinomas from the same iodine deficient geographic region was only 35% (82% diffuse and 18% nodular). 17.5% of acromegalic patients underwent thyroid surgery before diagnosis of growth hormone excess. 17.5% of acromegalic patients with goiters had autonomous areas in their thyroids and 5% were clearly hyperthyroid. Goiters developed slightly more often in females (74%) than in males (67%). The mean preoperative growth hormone level was higher in acromegalic patients with goiter. The incidence of goiters was positively correlated with the documented time of elevated growth hormone concentration in serum. Two patients with exaggerated response of thyrotropin (TSH) (delta TSH greater than 20 mU/l) to the application of thyrotropin-releasing hormone (TRH) had no goiters. On the other hand most patients (61%) with goiters had a low TSH-response to TRH (delta TSH less than 10 mU/l) representing in part occult autonomy of thyroid function. No patient with prolactinoma has had previous thyroid surgery nor thyroid autonomy. One patient with prolactinoma suffered from Graves' disease and none of the acromegalic patients had this disease. We finally conclude that the elevation of growth hormone leads to increased incidence of euthyroid and hyperthyroid (autonomous) goiters independently of the influence of TSH.

Papillary Thyroid Carcinoma without Metastases Manifesting as an Autonomously Functioning Thyroid Nodule

“…Therefore, higher TSH levels as the sole factor responsible for goiter appears to be an oversimplification [13]. Goiter should be regarded as a complex trait in which genetic susceptibility [13,16], enviromental factors [13], TSH, growth factors [13,17,18], and angiogenic substances [13,19,20] either play a distinct and separate role or act synergistically through complex interaction mechanisms [13]. However, the relative contributions of these factors to the goitrogenic process have yet to be clarified [13].…”

Growth factors and goitrogenesis

“…Acromegaly, characterised by elevated levels of serum IGF-I, has long been associated with goitre (>70% incidence; Wuster et al 1991). Minuto et al (1989) described a 2-fold increase in immunoreactive IGF-I in patients with MNTG compared with controls, but IGF-I levels were not elevated in goitres associated with Graves' disease.…”

Octreotide and Bromocriptine Suppress Thyroid Hormone Levels and Thyroid Nodule in an Acromegalic Patient with Nontoxic Autonomous Goiter.

“…In most acromegalic patients, TSH response to TRH is impaired due to the inhibition by excessive hypothalamic somatostatin, but complete suppression of TSH is rather rare in cases with preserved anterior pituitary functions. Wi ster et al [5] showed that 10 out of 80 patients with acromegaly had thyroid autonomies. Gemsenjager et al [12] reported that some patients with nontoxic multinodular goiter showed no TSH response to TRH, suggested a state of preclinical hyperthyroidism.…”

“…patients, several abnormalities related to the thyroid and the pituitary-thyroid axis, such as goiter formation, changes in serum thyroid hormone levels and impaired TSH response to TRH, have been described [1][2][3][4][5][6]. In most studies, serum T4i ]T3 and basal TSH levels are found to be normal.…”