Pituitary-hormone secretion by thyrotropinomas

Thyrotropin-secreting microadenoma and the importance of a prompt diagnosis: A case report

Background

The prevalence of thyrotropin-secreting pituitary adenomas, most being macroadenomas, is one to two cases per million inhabitants. Their differential diagnosis may be challenging, especially for microadenomas.

Case description

We present the case of a 50-year-old male with progressive neck enlargement, hot sudorific hands, anorexia, diarrhea, and weight loss over the preceding three months. Laboratory evaluation revealed high thyroid hormones, predominantly high free triiodothyronine of 7.74 pg/mL (reference range 2.3-4.2), with a non-suppressed thyroid stimulating hormone (TSH) of 1.73 µIU/mL (reference range 0.55-4.78). A high level of suspicion directed additional evaluation that revealed a high total alpha-subunit of glycoprotein hormones (αGS) and αGS/TSH ratio. Magnetic resonance imaging revealed a six mm pituitary lesion. A microthyrotropinoma was diagnosed, and long-acting octreotide was initiated before surgery for symptomatic control. Endoscopic transnasal transsphenoidal tumor resection was performed months later. The patient was in remission one year after surgery with no pituitary deficits.

Conclusions

Reaching an accurate diagnosis on time is crucial for deciding the optimal therapeutic approach and preventing and decreasing the frequency of endocrine and neurological complications. HIPPOKRATIA 2022, 26 (4):157-160.

Hormone secretion by pituitary adenomas is characterized by increased disorderliness and spikiness but more regular pulsing

CONTEXT

Hormone secretion by functioning pituitary tumors is characterized by increased basal (nonpulsatile) secretion, enhanced pulse frequency, amplified pulse mass, and increased disorderliness.

OBJECTIVE

The objective of the study was to quantify (subtle) abnormalities of hormone secretion by pituitary adenomas and the influence of selective pituitary surgery and suppressive medications on these parameters.

METHODS

Approximate entropy (ApEn) was quantified with a refined algorithm, spikiness by a new method to evaluate sudden short-lived increases in hormone levels, and pulsing regularity, determined with a fully automated deconvolution program. These 3 distinct measures of secretory disruption were compared in untreated and treated patients with acromegaly, prolactinoma, and Cushing's disease together with matching profiles in healthy controls.

RESULTS

ApEn and spikiness were markedly increased in all untreated patient groups and normalized after pituitary surgery in acromegaly and hypercortisolism. In contrast, hormone-suppressive medical treatment in acromegaly and prolactinoma did not normalize ApEn. Spikiness normalized in acromegalic patients but not in prolactinoma. GH and cortisol pulsing regularity was elevated in acromegaly and Cushing's disease, respectively, and normalized after surgery. Medical treatment caused normalization of pulsing regularity in acromegaly but not in prolactinoma patients.

CONCLUSION

This study extends the understanding of disorganized hormone secretion by hyperfunctioning pituitary adenomas. The new findings are increased spikiness in all 3 tumor groups and increased pulsing regularity in GH- and ACTH-secreting adenomas. The mechanisms behind the marked pattern irregularity and the selective normalization by surgical and medical therapies are not established yet but may include diminished feedback signaling in addition to the anatomical and functional disorganization of intrapituitary cell networks.

A long-term follow-up study of eighteen patients with thyrotrophin-secreting pituitary adenomas

OBJECTIVE

TSH-secreting pituitary adenomas (TSH-omas) are a rare cause of thyrotoxicosis. First-line therapy for these tumours is neurosurgery, although medical therapy with somatostatin analogues (SSAs) is increasingly used for this indication.

DESIGN AND PATIENTS

We retrospectively reviewed the data of patients with a TSH-oma (n = 18, 67% males) followed between 1989 and 2011 (median follow-up 7 years, range 1-21) in three academic medical centres in the Netherlands, focusing on the role of SSA treatment.

MEASUREMENTS

Patient records were reviewed for clinical, biochemical, imaging, pathological and treatment characteristics.

RESULTS

At initial evaluation, biochemical hyperthyroidism with non-suppressed TSH concentrations was detected in 94% of the patients. The majority of patients (72%) had a macroadenoma with extrasellar extension. Fourteen patients underwent surgery, resulting in postoperative euthyroidism in six patients (43%). Recurrence of hyperthyroidism developed in three of them after 5, 24 and 32 months, respectively. Adjuvant radiotherapy (n = 2) did not induce remission. Three patients received SSA therapy exclusively, resulting in apparent cure in one of them. During long-term follow-up, 72% of all patients required medical therapy (mostly SSA treatment). Euthyroidism was achieved in all but one patient, who refused all treatments.

CONCLUSIONS

Our results demonstrate that patients with TSH-omas, who often present with large macroadenomas with extrasellar extension, have an excellent response to SSA therapy. Because the results of surgery and radiotherapy are disappointing, primary medical therapy may be considered in virtually all patients, except in case of optic chiasm compression, especially in those harbouring large adenomas with parasellar extension.

Thyrotropin-secreting pituitary tumor presenting with congestive heart failure and good response to dopaminergic agonist cabergoline

Hyperthyroidism is an important inducing factor in patients with atrial fibrillation, and may trigger heart failure. Thyrotropin (thyroid stimulating hormone, TSH)-secreting pituitary tumors are rare causes of hyperthyroidism. Here, we report a 66-year-old man with a pituitary TSH-secreting tumor who presented with hyperthyroidism and congestive heart failure. Endonasal trans-sphenoidal pituitary adenomectomy was performed. After the operation, the symptoms of hyperthyroidism and congestive heart failure were relieved, associated with normalization of thyroid function tests. Unfortunately, hand tremor and progressively elevated free T4 and TSH concentrations recurred 5 months after surgery. A dopaminergic agonist, cabergoline was administered and euthyroidism was restored for at least 11 months.

Thyrotropinoma and multinodular goiter: A diagnostic challenge for hyperthyroidism

Thyroid disorders are frequently encountered. The diagnosis is straightforward unless clinical or laboratory findings are inconclusive and/or perplexing. Hyperthyroidism due to a thyrotropin-secreting pituitary adenoma rarely occurs and symptoms due to thyroid hormone excess are subtle. The presentation of the disease becomes unusual when co-secretion of other hormones with thyrotropin or concomitant thyroid parenchymal pathology exist. We present the case of a 63-year-old female patient with thyrotropinoma co-secreting growth hormone and multinodular goiter. She developed hyperthyroidism first due to thyrotropinoma and later due to a toxic nodule. Herein, we discuss the diagnostic and therapeutic challenges of hyperthyroidism with atypical presentation.

Thyrotropin secretion patterns in health and disease

Thyroid hormones are extremely important for metabolism, development, and growth during the lifetime. The hypothalamo-pituitary-thyroid axis is precisely regulated for these purposes. Much of our knowledge of this hormonal axis is derived from experiments in animals and mutations in man. This review examines the hypothalamo-pituitary-thyroid axis particularly in relation to the regulated 24-hour serum TSH concentration profiles in physiological and pathophysiological conditions, including obesity, primary hypothyroidism, pituitary diseases, psychiatric disorders, and selected neurological diseases. Diurnal TSH rhythms can be analyzed with novel and precise techniques, eg, operator-independent deconvolution and approximate entropy. These approaches provide indirect insight in the regulatory components in pathophysiological conditions.

Hyperthyroidism caused by an ectopic thyrotropin-secreting tumor of the nasopharynx: a case report and review of the literature

BACKGROUND

Ectopic thyrotropin (TSH)-secreting tumors are extremely rare. To our knowledge, only three cases have previously been reported so far, but the tumors were not studied ultrastructurally and in vitro. We present a case that was extensively examined to gain deeper insights in terms of the histopathological features and hormonal secretion profile of the tumor.

PATIENT FINDINGS

A 49-year-old female complained of nasal obstruction for 15 years and thyrotoxicosis for one and a half years. Except for a high basal TSH with concomitantly elevated free tri-iodothyronine (FT3) and free thyroxine (FT4) levels, her pituitary hormone profile yielded normal results. Magnetic resonance imaging revealed a 2 cm × 2 cm mass in the nasopharynx, which showed an increased tracer uptake on octreotide scintigraphy. Preoperative treatment with octreotide effectively reduced serum TSH, FT3, and FT4 to normal levels. The mass was endoscopically removed via an endonasal approach. Immunophenotyping and hormone determination of cultured cells confirmed that the mass was a plurihormonal TSH-/growth hormone (GH)-/prolactin (PRL)-producing adenoma. Co-expression of TSH and GH was found in most cells. Electron microscopy showed that the adenoma was formed by a single cell type, with secretory granules of small size. In vitro studies demonstrated that octreotide reduced both TSH and GH secretion.

SUMMARY

We report an ectopic TSH-secreting tumor, which had plurihormonal secretion in vitro, including TSH, GH, and PRL. Histologically, it mimicked a TSH-secreting pituitary adenoma. Octreotide was useful in the diagnosis and treatment of this ectopic TSH-secreting tumor.

CONCLUSIONS

Ectopic TSH-secreting tumors are extremely rare. In terms of hormone secretion profile, histological characteristics, and response to octreotide, they are similar to pituitary TSH-secreting adenomas, suggesting that they are of identical cell origin.