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Ectopic TSH-secreting pituitary tumor: a case report and review of prior cases.

Song M, Wang H, Song L, Tian H, Ge Q, Li J, Zhu Y, Li J, Zhao R, Ji HL - BMC Cancer (2014)

Bottom Line: TRH stimulating test was negative, whereas octreotide inhibition test showed a reduction in TSH by 30.8%.Furthermore, a large space-occupying lesion located at the nasopharynx was found by computed tomography and magnetic resonance imaging (MRI).The characteristics and successful interventions summarized in this report provide a guideline for clinicians.

View Article: PubMed Central - PubMed

Affiliation: Department of Endocrinology, Weihai Municipal Hospital, 70 Heping Road, Weihai, Shandong 264200, China. whsmq1201@hotmail.com.

ABSTRACT

Background: Ectopic TSH-secreting pituitary adenoma (TSH-oma) is a very unusual disorder. To date, there are only four cases reported. It is difficult to distinguish ectopic cases from both regular TSH-omas and resistance to thyroid hormone (RTH).

Case presentation: A newly identified case of ectopic TSH-oma arising from the nasal pharynx was described, and reports of four prior cases were reviewed. The patient was a 41-year-old male who developed what appeared to be typical hyperthyroidism and atrial fibrillation in 2009. Thyroid function tests showed elevated basal levels of free T3 (FT3, 24.08 pmol/L), free T4 (FT4, 75.73 pmol/L), and serum TSH (7.26 μIU/ml). Both TSH-oma and resistance to thyroid hormone syndrome were considered. TRH stimulating test was negative, whereas octreotide inhibition test showed a reduction in TSH by 30.8%. Furthermore, a large space-occupying lesion located at the nasopharynx was found by computed tomography and magnetic resonance imaging (MRI). A normal pituitary was visualized. Ectopic TSH-oma was preliminarily established. Using an endoscopic endonasal approach, the tumor was resected. Histological features and immunophenotypes were consistent with those of TSH-secreting tumor. The levels of both free thyroxine and TSH returned to normal ranges the day after surgery and remained within normal range for 48 months.

Conclusions: Although exceedingly rare, ectopic TSH-oma should be considered for patients with inappropriate secretion of TSH with hyperthyroidism and pituitary tumor undetectable by computed tomography and MRI. To our knowledge, this is the first case followed up more than 4 years. The characteristics and successful interventions summarized in this report provide a guideline for clinicians.

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Differential diagnosis of TSH-omas. α-GSU, α-glycoprotein hormone subunits; SHBG, sex-hormone binding globulin; TRH, thyroptroin releasing hormone; TRβ, thyroid hormone receptor β.
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Fig4: Differential diagnosis of TSH-omas. α-GSU, α-glycoprotein hormone subunits; SHBG, sex-hormone binding globulin; TRH, thyroptroin releasing hormone; TRβ, thyroid hormone receptor β.

Mentions: It is not easy to distinguish TSH-oma from resistance to thyroid hormones (RTH) (Figure 4). RTH is rare, more than 90% of RTH are hereditary, displaying autosomal dominant inheritance, which are linked to mutations of thyroid hormone receptor β gene. RTH also exhibits high FT3 and FT4 levels and inappropriate TSH secretion. In addition, there were no significant differences in the basal values of TSH and free thyroid hormones between TSH-secreting tumor and RTH [11, 12]. Hence, other diagnostic measures are required. Glycoprotein hormone subunits (α-GSU) and molar ratio of α-GSU/TSH are valuable indicators to distinguish TSH-secreting tumor from RTH. More than 80% of TSH-secreting tumors had hypersecretion of circulating free α-GSU and an elevated α-GSU/TSH molar ratio [9, 12, 13]. It was more common in macroadenomas than in micro-adenomas [9]. The pituitary adenoma causing hyperthyroidism is composed of two types of cells, one secreting α-GSU alone, and the other producing both α-GSU and thyrotropin but not in equal amounts [14]. Generally, α-GSU is secreted more than TSH. However, in this case, α-GSU was not detected. Furthermore, TSH-oma displayed an elevation in sex-hormone-binding globulin, while it was normal in RTH [12]. The final diagnosis was made by TRH stimulating and octreotide inhibition tests. While 96% of TSH-secreting tumor presented a blunted TSH response to the TRH test and 97% of RTH were excited by TRH [12]. This patient presented a blunted TSH response to the TRH test (Figure 2A). Most pituitary TSH-secreting tumor cells possess somatostatin receptors, which are sensitive to somatostatin and its analogues. FT3 and FT4 levels decreased markedly following delivery of somatostatin analogues in all TSH-omas but not RTH patients [12]. Similarly, the inhibitory effect of octreotide was seen in ectopic TSH-oma too [5]. This patient presented a significant inhibitory response to octreotide (Figure 2B), and the inhibitory effect of octreotide on ectopic TSH-oma cells was also confirmed in vitro [5]. In addition, TSH-secreting tumor cells possessed dopamine receptors. The presence of dopamine receptors in TSH-omas was the rationale for therapeutic trials with dopaminergic agonists. Several studies, however, have shown a large heterogeneity of TSH responses to dopaminergic agents [13, 15]. In fact, administration of dopamine agonists failed to persistently block TSH secretion in almost all patients and caused tumor shrinkage only in those with combined hypersecretion of TSH and PRL [16].Figure 4


Ectopic TSH-secreting pituitary tumor: a case report and review of prior cases.

Song M, Wang H, Song L, Tian H, Ge Q, Li J, Zhu Y, Li J, Zhao R, Ji HL - BMC Cancer (2014)

Differential diagnosis of TSH-omas. α-GSU, α-glycoprotein hormone subunits; SHBG, sex-hormone binding globulin; TRH, thyroptroin releasing hormone; TRβ, thyroid hormone receptor β.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4125694&req=5

Fig4: Differential diagnosis of TSH-omas. α-GSU, α-glycoprotein hormone subunits; SHBG, sex-hormone binding globulin; TRH, thyroptroin releasing hormone; TRβ, thyroid hormone receptor β.
Mentions: It is not easy to distinguish TSH-oma from resistance to thyroid hormones (RTH) (Figure 4). RTH is rare, more than 90% of RTH are hereditary, displaying autosomal dominant inheritance, which are linked to mutations of thyroid hormone receptor β gene. RTH also exhibits high FT3 and FT4 levels and inappropriate TSH secretion. In addition, there were no significant differences in the basal values of TSH and free thyroid hormones between TSH-secreting tumor and RTH [11, 12]. Hence, other diagnostic measures are required. Glycoprotein hormone subunits (α-GSU) and molar ratio of α-GSU/TSH are valuable indicators to distinguish TSH-secreting tumor from RTH. More than 80% of TSH-secreting tumors had hypersecretion of circulating free α-GSU and an elevated α-GSU/TSH molar ratio [9, 12, 13]. It was more common in macroadenomas than in micro-adenomas [9]. The pituitary adenoma causing hyperthyroidism is composed of two types of cells, one secreting α-GSU alone, and the other producing both α-GSU and thyrotropin but not in equal amounts [14]. Generally, α-GSU is secreted more than TSH. However, in this case, α-GSU was not detected. Furthermore, TSH-oma displayed an elevation in sex-hormone-binding globulin, while it was normal in RTH [12]. The final diagnosis was made by TRH stimulating and octreotide inhibition tests. While 96% of TSH-secreting tumor presented a blunted TSH response to the TRH test and 97% of RTH were excited by TRH [12]. This patient presented a blunted TSH response to the TRH test (Figure 2A). Most pituitary TSH-secreting tumor cells possess somatostatin receptors, which are sensitive to somatostatin and its analogues. FT3 and FT4 levels decreased markedly following delivery of somatostatin analogues in all TSH-omas but not RTH patients [12]. Similarly, the inhibitory effect of octreotide was seen in ectopic TSH-oma too [5]. This patient presented a significant inhibitory response to octreotide (Figure 2B), and the inhibitory effect of octreotide on ectopic TSH-oma cells was also confirmed in vitro [5]. In addition, TSH-secreting tumor cells possessed dopamine receptors. The presence of dopamine receptors in TSH-omas was the rationale for therapeutic trials with dopaminergic agonists. Several studies, however, have shown a large heterogeneity of TSH responses to dopaminergic agents [13, 15]. In fact, administration of dopamine agonists failed to persistently block TSH secretion in almost all patients and caused tumor shrinkage only in those with combined hypersecretion of TSH and PRL [16].Figure 4

Bottom Line: TRH stimulating test was negative, whereas octreotide inhibition test showed a reduction in TSH by 30.8%.Furthermore, a large space-occupying lesion located at the nasopharynx was found by computed tomography and magnetic resonance imaging (MRI).The characteristics and successful interventions summarized in this report provide a guideline for clinicians.

View Article: PubMed Central - PubMed

Affiliation: Department of Endocrinology, Weihai Municipal Hospital, 70 Heping Road, Weihai, Shandong 264200, China. whsmq1201@hotmail.com.

ABSTRACT

Background: Ectopic TSH-secreting pituitary adenoma (TSH-oma) is a very unusual disorder. To date, there are only four cases reported. It is difficult to distinguish ectopic cases from both regular TSH-omas and resistance to thyroid hormone (RTH).

Case presentation: A newly identified case of ectopic TSH-oma arising from the nasal pharynx was described, and reports of four prior cases were reviewed. The patient was a 41-year-old male who developed what appeared to be typical hyperthyroidism and atrial fibrillation in 2009. Thyroid function tests showed elevated basal levels of free T3 (FT3, 24.08 pmol/L), free T4 (FT4, 75.73 pmol/L), and serum TSH (7.26 μIU/ml). Both TSH-oma and resistance to thyroid hormone syndrome were considered. TRH stimulating test was negative, whereas octreotide inhibition test showed a reduction in TSH by 30.8%. Furthermore, a large space-occupying lesion located at the nasopharynx was found by computed tomography and magnetic resonance imaging (MRI). A normal pituitary was visualized. Ectopic TSH-oma was preliminarily established. Using an endoscopic endonasal approach, the tumor was resected. Histological features and immunophenotypes were consistent with those of TSH-secreting tumor. The levels of both free thyroxine and TSH returned to normal ranges the day after surgery and remained within normal range for 48 months.

Conclusions: Although exceedingly rare, ectopic TSH-oma should be considered for patients with inappropriate secretion of TSH with hyperthyroidism and pituitary tumor undetectable by computed tomography and MRI. To our knowledge, this is the first case followed up more than 4 years. The characteristics and successful interventions summarized in this report provide a guideline for clinicians.

Show MeSH
Related in: MedlinePlus