Long term treatment with the somatostatin analog SMS 201-995 in a patient with a thyrotropin- and growth hormone-secreting pituitary adenoma

TSH-Secreting Pituitary Adenoma: Current Management and Review

The neurosurgical literature contains little information about the current management of patients with thyroid-stimulating hormone (TSH)-secreting pituitary adenomas or about the usefulness of the somatostatin analogue octreotide in such cases. While TSH-secreting pituitary adenomas are rare, our review and illustrative case demonstrate the effectiveness of pretreating patients with octreotide therapy not only to reduce tumor size prior to surgical resection but also to increase the possibility of clinical remission.A 52-year-old male presented with signs and symptoms of hyperthyroidism and elevated TSH, thyroxine, and triiodothyronine. Magnetic resonance imaging revealed a pituitary macroadenoma with extension into the suprasellar cistern. The patient was treated with octreotide for 6 months prior to surgery. Approximately 3 months after initiation of octreotide therapy, the patient exhibited excellent biochemical and clinical response. Tumor shrinkage of nearly 50% was associated with resolution of suprasellar extension and optic nerve compression. Subsequent transsphenoidal surgery for resection of residual adenoma was followed by symptomatic and hormonal remission without the need for reinstitution of octreotide therapy.Pretreatment with octreotide for TSH-secreting pituitary adenomas has a beneficial effect on disease symptoms and reduces tumor mass. We suggest that patients with these rare tumors can be managed with a combination of octreotide therapy and subsequent surgical removal of residual tumor. Although this combination treatment helps to facilitate clinical remission, only short-term follow-up has been reported and thus the optimal management of these patients remains to be determined.

Medical therapy of pituitary adenomas: effects on tumor shrinkage

The efficacy of dopamine-agonists (DA) in patients with prolactinomas and that of somatostatin analogues (SSA) in those with GH- and TSH-secreting adenomas is well established. More recently, data are accumulating suggesting a potential therapeutic role of DA also in patients with ACTH-secreting and clinically non-functioning (NFA) pituitary adenomas. This review aims at summarizing published results of DA and SSA on tumor shrinkage in patients with different histotypes of pituitary adenomas. Results of tumor shrinkage are of clinical relevance as tumor size is the one of the most important determinant of surgical outcome. While reduction of tumor size more than 50% of baseline size in macroprolactinomas treated with DA is a frequent finding in patients with GH-secreting adenomas treated with SSA tumor shrinkage only recently is becoming frequent thanks to the availability of depot formulations. Data on tumor shrinkage in patients with TSH-secreting adenomas treated with SSA are limited because of the rarity of these tumors. Very recently, DA have been reported of some efficacy also in patients with ACTH-secreting adenomas but data are still very limited. NFA respond very scantly to both DA and SSA even if receptors targeting these drugs are present. Whether this is due to limited receptor number or alterations of post-receptor pathway is still unknown.

Expression of type 5 somatostatin receptor in TSH-secreting pituitary adenomas: a possible marker for predicting long-term response to octreotide therapy

In TSH-secreting pituitary adenomas (TSHoma), octreotide (OCT) therapy reduces tumor size and TSH secretion in some cases but not in others. As OCT acts through various types of somatostatin receptors (SSTRs), the different responses of TSHoma to OCT might be explained by the differences of SSTR expression. We therefore studied the expression of subtype-specific SSTR mRNA transcripts in tumor tissues by RT-PCR. Type 2 (SSTR2) mRNA transcripts were detected in all 8 tumors but those of SSTR3 and SSTR5 were demonstrated only in 5 of them. Serum TSH levels were decreased by OCT administration test in all patients but OCT therapy was effective in two patients out of three. SSTR5 mRNA was detected in two tumors from the responder, but not in one tumor that was resistant to OCT. These observations suggest that the temporal decrease of TSH by OCT may be mediated by SSTR2, and that the long term response to OCT therapy may be related with the expression of SSTR5. Therefore, the expression of SSTR5 in TSHoma may be a useful marker for predicting the outcome of the therapy, but further studies with larger numbers of patients are necessary.

Evaluation of the treatment of thyrotropin-secreting pituitary adenomas with a slow release formulation of the somatostatin analog lanreotide

Somatostatin analogs have been shown to be effective for the treatment of TSH-secreting pituitary adenomas. However, their use in this indication is limited by the fact that available analogs require several daily sc injections. The present study was performed to evaluate the effects of a slow release formulation of the somatostatin analog lanreotide (SR-L) on both hormone secretion and tumor size and to assess the tolerance in a series of thyrotropinomas treated for 6 months. Eighteen patients with hyperthyroidism related to a TSH-secreting pituitary adenoma, evidenced by pituitary magnetic resonance imaging, were studied. After a basal assessment, each patient received 30 mg SR-L, im, every 14 days for 1 month. Then, according to the free T3 (fT3) plasma level measured, 9 of 18 patients were injected twice monthly, and 7 of 18 patients received SR-L every 10 days for 5 additional months. One patient was dismissed from the study in month 1 of the study for side-effects and another in month 3 for noncompliance to the protocol. Clinical and biological evaluations (plasma TSH, free alpha-subunit, fT4, fT3, and lanreotide levels) were performed before and in months 1, 3, and 6 of treatment. Pituitary magnetic resonance imaging and gallbladder ultrasonography were performed both at entry and at the end of the study. Clinical signs of hyperthyroidism improved within 1 month in all 16 evaluable patients. Mean (+/- SEM) plasma lanreotide levels reached 1.11 +/- 0.43 and 1.69 +/- 0.65 ng/mL in month 3 using 2 and 3 injections/month, respectively, then remained stable until the end of the study. During therapy, the plasma TSH level decreased from 2.72 +/- 0.32 to 1.89 +/-0.27 mU/L (P < 0.01), with parallel significant changes in free alpha-subunit. During the same period, plasma fT4 and fT3 levels decreased from 37.9 +/- 2.9 to 19.7 +/- 2.3 pmol/L (P < 0.01) and from 14.6 +/- 1.1 to 8.3 +/- 0.8 pmol/L (P < 0.01), respectively. No statistically significant change in mean adenoma size was observed after 6 months of treatment. Side-effects, including pain at the injection point, abdominal cramps, and diarrhea, were mild and transient and did not lead to interruption of the treatment. No gallstones occurred during the study. SR-L appears to be able to suppress clinical signs of hyperthyroidism in our series of patients with TSH-secreting pituitary adenomas. The analog also reduces plasma TSH and thyroid hormone levels, which were normalized in 13 of 16 cases. The effect was maintained throughout the treatment using 2 or 3 SR-L injections monthly without any problem of tolerance. We conclude that SR-L is a safe and effective treatment of thyrotropinomas and avoids the drawbacks of the modes of administration of other somatostatin analogs, given three times daily.

Long-standing goiter and hypothyroidism: an unusual presentation of a TSH-secreting adenoma

A 63-year-old female patient was referred to our hospital in February 1994 for a pituitary tumor. On a previous examination, in 1973, she had a goiter, nonspecific symptoms and only an elevated serum T3. In 1984 she had become hypothyroid, her goiter had increased, serum T4 was 69 nmol/L, TSH 34.4 mU/L, and TPO antibodies were positive. Hypothyroidism due to autoimmune thyroiditis was diagnosed and she received L-T4 100 micrograms/day. In 1985 and 1986, serum TSH had decreased but remained slightly elevated, while T4 was at the upper limits of normal. From 1987 to 1989 her serum TSH rose from 9 to 20 mU/L and remained at that level for the ensuing 4 years in spite of increasing L-T4 up to 150 micrograms/day. In October 1993, after discontinuing L-T4 for 6 weeks, TSH was 23.7 mU/L, T4 170 nmol/L, 131I thyroid uptake 52%, and the CT scan showed a large pituitary tumor with suprasellar extension. On preoperative investigation TSH was 40-51 mU/L with no response to TRH or GnRH. The alpha-subunit was increased at 6.33 micrograms/L with the alpha-TSH/TSH molar ratio of 1.23. Prolactin was elevated, but plasma cortisol, FSH, and LH were low. At surgery, we found a large chromophobe adenoma with few PAS-positive granules and with immunostaining positive for TSH and prolactin. From the clinical and biological data, we can conclude that the patient had probably a TSH-secreting adenoma since the goiter was first detected. The development, however, of autoimmune thyroiditis with hypothyroidism considerably modified the presentation of the disease and may have accelerated the growth of the tumor.

Effects of a slow-release formulation of the new somatostatin analogue lanreotide in TSH-secreting pituitary adenomas

OBJECTIVE

Somatostatin analogues have been proposed for the treatment of thyrotrophinomas. However, this treatment requires several s.c. injections a day to be effective. The present study had the following aims: (i) appraisal of the efficacy of a single dose of two somatostatin analogues (lanreotide and octreotide) to acutely inhibit TSH secretion of TSH-secreting pituitary adenomas; (ii) assessment of the efficacy of a single injection of a slow release formulation of lanreotide (SR-L) in reducing TSH and thyroid hormone secretions in the same cases; and (iii) evaluation of the effects of SR-L used for 3-6 months on hormone secretion and tumour size.

PATIENTS

Four patients with hyperthyroidism linked to a TSH-secreting pituitary adenoma found on pituitary magnetic resonance imaging (MRI) and subsequently proved by immunohistochemistry were studied.

METHODS

In the first step of the study the patients received in a random order, vehicle, 150 micrograms octreotide and 500 micrograms lanreotide as a single s.c. injection. Measurements of plasma TSH, free T4 (fT4), free T3 (fT3) and free alpha subunit (fAS) levels were carried out before injection and then every other hour for 8 hours. In the second part of the study, after a basal blood sample (0800 h), each patient received 30 mg lanreotide as an i.m. injection of SR-L. Blood was sampled 2 hours later and then three times a week for 3 weeks in order to measure plasma TSH, fT4, fT3 and lanreotide levels using radioimmunoassays. The patients then received one SR-L injection twice or in one case three times a month for 3-6 months. Plasma TSH, fT4 and fT3 levels were measured monthly and a pituitary MRI was performed at the end of the treatment with SR-L.

RESULTS

500 micrograms lanreotide acutely reduced plasma TSH and fAS levels to the same extent as 150 micrograms octreotide. Two hours after a single i.m. injection of SR-L plasma lanreotide levels reached 7.8 +/- 0.6 micrograms/l and then progressively decreased, being 1.8 +/- 0.2 microgram/l on day 2 and 1.1 +/- 0.3 microgram/l on day 14 after the injection. Plasma TSH level decreased from basal value (mean +/- SEM 4.4 +/- 1.2 mlU/l) within 2 hours (2.5 +/- 0.8 mlU/l) and further declined to 0.8 +/- 0.2 ml/Ul on day 2 following the injection. Depending on the patient, plasma TSH levels were reduced for a period of 6-15 days. Plasma fT4, fT3 levels were normalized on day 2 and remained in the normal range for a period of time of 9-20 days. During long-term treatment, abdominal cramps and diarrhoea appeared, leading to interruption of the treatment in one patient. The treatment was well tolerated in the other three patients. Plasma TSH and thyroid hormone levels progressively decreased during the treatment. No change in adenoma volume was observed after 3-6 months of therapy.

CONCLUSIONS

This study shows that (i) lanreotide is able to inhibit acutely TSH secretion in thyrotrophinomas and that a single s.c. injection of 500 micrograms lanreotide is as effective as 150 micrograms octreotide; (ii) SR-L appears to be able to reduce plasma TSH and to normalize fT4 and fT3 levels for 9-20 days in patients with thyrotrophinomas; (iii) this effect is maintained throughout the treatment using two or three SR-L injections monthly for months. These results suggest that SR-L could be used as a treatment of thyrotrophinomas and avoids the drawbacks of the modes of administration of other somatostatin analogues used in such cases.

Treatment of thyroid-stimulating hormone-secreting adenomas with octreotide

From data collected in the literature, the effects of octreotide therapy in 37 patients with thyroid-stimulating hormone (TSH)-secreting adenomas who received short-term (1 to 2 weeks, n = 23) and long-term treatment (3 to 36 months) are reviewed. In 20 of 21 patients studied, short-term administration of octreotide (50 or 100 micrograms subcutaneously [SC] produced a 25% to 100% (mean +/- SD, 55.3% +/- 29%) decrease in TSH levels, with the nadir being obtained between the third and sixth hour following injection. After 1 to 2 weeks therapy with 50 to 100 micrograms twice or three times a day, 21 of 23 patients studied demonstrated a 66% (+/- 30%) decrease in TSH levels and 14 of 16 showed a 64% (+/- 27%) decrease in alpha-subunit levels. In approximately two thirds of the patients, the response was better than after short-term administration. The effect of octreotide on clinical and biological thyroid status was significant in all patients studied. After 1 week or 1 month of treatment, thyroid hormone levels were reduced in all patients and were normalized in 78%. Response to therapy was similar whether TSH secretion was pure or mixed (growth hormone [GH]-TSH adenomas). Fourteen patients received long-term treatment (3 to 36 months; mean, 12 +/- 10) with daily doses ranging from 200 to 1,500 micrograms. The response was better than or similar to that with short-term treatment. An escape occurred in TSH levels in two patients and in thyroid hormone levels in three patients, leading to an adjustment of dose or frequency of injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperthyroidism due to inappropriate secretion of thyrotropin in 10 patients

PURPOSE

The syndrome of inappropriate thyroid-stimulating hormone (TSH) secretion, characterized by elevated serum free thyroxine and triiodothyronine levels in association with measurable serum TSH concentrations, remains an uncommon cause of hyperthyroidism that is being recognized with increasing frequency. The hyperthyroidism may be due to either neoplastic pituitary TSH secretion or selective pituitary resistance to thyroid hormone. In an effort to better understand this rare cause of hyperthyroidism, we undertook a retrospective analysis of our institution's experience with this condition.

PATIENTS

We reviewed our cumulative experience (10 patients) with hyperthyroidism due to the syndrome of inappropriate secretion of TSH.

RESULTS

Six patients were diagnosed with TSH-secreting pituitary adenomas and four were found to have selective pituitary resistance to thyroid hormone. One patient with tumor had a TSH-secreting pituitary adenoma in the setting of multiple endocrine neoplasia syndrome. In all patients with tumor, hyperthyroidism was successfully treated with transsphenoidal adenomectomy with or without pituitary radiotherapy. All four patients with pituitary resistance had thyroid ablation or resection prior to their correct diagnosis. Therefore, therapy for this group of patients involved thyroid hormone replacement and efforts to suppress TSH hypersecretion. All 10 patients have done well clinically, with follow-up ranging from 2 weeks to 13 years.

CONCLUSIONS

Adequate treatment exists for the two primary causes of TSH hypersecretion. TSH-secreting pituitary adenomas are treated with surgery and, if necessary, adjuvant pituitary radiotherapy. The results are generally good if the tumor is diagnosed and treated at an early stage. Primary therapy for hyperthyroidism due to selective pituitary resistance to thyroid hormone is aimed at suppression of pituitary TSH hypersecretion. The evaluation of any patient with hyperthyroidism must be thorough and, in some cases, should include measurement of TSH to determine the presence of inappropriate secretion. Eliminating this diagnosis will help avoid improper and potentially harmful treatment of hyperthyroid patients.

Four year treatment with a long acting somatostatin analogue in a patient with Verner-Morrison syndrome

The case is described of a woman with a Verner-Morrison syndrome of extreme severity, caused by an occult VIPoma. Administration of SMS 201-995 (Sandoz) (SMS) at the dose of 150 and subsequently of 250 micrograms daily, decreased plasma levels of vasoactive intestinal polypeptide (VIP) from about 500 to 100 pg/ml (highest normal limit 60 pg/ml). This was associated with complete regression of the diarrhea and normalization of serum potassium levels and hence with the return of the patient to a fully normal life. After 36 months of clinical remission, watery diarrhea recurred together with elevation of VIP plasma levels and appearance of liver metastases. Laparotomic exploration led to the removal of a pancreatic VIPoma and its liver secondarisms, which was followed by a second remission. Reappearance of the symptoms and development of new liver metastases 8 months later required reinstitution of SMS therapy, which allowed once again to control the clinical picture. Anterior pituitary function, assessed by dynamic testing, was unaffected by chronic SMS administration with the exception of the stimulated growth hormone secretion that was inhibited. Glucose tolerance and insulin secretion remained normal during treatment. Glucose intolerance ensued after pancreatectomy and was not worsened by reintroduction of SMS. Treatment with SMS may allow long-lasting remission of Verner-Morrison syndrome associated to VIPoma, though it does not arrest the progression of the tumor.

Surgical treatment of thyrotropin-secreting pituitary adenomas

Thyrotropin-secreting pituitary adenomas have been diagnosed more frequently as radiographic techniques and biochemical assays have improved; however, they remain uncommon and are unfamiliar to most neurosurgeons. This report concerns eight patients with hyperthyroidism, inappropriately elevated levels of serum thyrotropin and alpha-subunit, and radiographic evidence of pituitary tumor. All underwent surgery and had pathological confirmation of a thyrotropin-secreting adenoma, and most had been subjected to prior ablation of the thyroid gland. Only one tumor was a microadenoma; the others ranged in size from 1.4 to 12 cm, and invasion of parasellar structures was common. Thyrotropin, triiodothyronine, thyroxine, and alpha-subunit were measured preoperatively and at intervals postoperatively. Coexistent hormonal abnormalities (which occurred in all patients) included acromegaly and hyperprolactinemia and were also monitored. All four patients who had tumors less than 2 cm in diameter remain alive. Complete extirpation of tumor in these patients produced rapid correction of all hormonal abnormalities and resolution of clinical hyperthyroidism. The other four patients had larger invasive tumors: two died soon after surgery, one died of disseminated tumor 8 years after presentation, and one remains alive with residual tumor. Tumors secreting thyroid-stimulating hormone are less easily cured by surgery than are other types of pituitary adenoma because of the large size and invasive features that many attain during the delay to diagnosis; medical therapy can subdue the tumor but not cure it. The experience with these patients establishes the importance of early diagnosis and surgical excision for successful treatment, and demonstrates the utility of modern diagnostic techniques for finding these lesions. As occurs in Nelson's syndrome after adrenalectomy for Cushing's disease, ablation of the target organ may allow the tumor to convert to a more clinically malignant form which is resistant to cure.

Octreotide. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in conditions associated with excessive peptide secretion

Octreotide is an analogue of somatostatin. Like endogenous somatostatin, it exerts a potent inhibitory effect on the release of anterior pituitary growth hormone and thyroid-stimulating hormone, and peptides of the gastroenteropancreatic endocrine system, while overcoming some of the shortcomings of exogenously administered somatostatin, namely a short duration of action, a need for intravenous administration and postinfusion rebound hypersecretion of hormone. Clinical studies have shown that octreotide is effective in the treatment of acromegaly and thyrotrophinomas. In comparative trials octreotide was significantly superior to bromocriptine in patients with acromegaly. Octreotide also appears to provide a significant advantage over existing therapies in the management of the carcinoid syndrome and offers considerable therapeutic potential in reversing carcinoid crises which may be life-threatening. Trials in patients with tumours producing vasoactive intestinal peptide demonstrated that octreotide may be an effective first-line choice for this condition, which has usually metastasised and become refractory to traditional symptomatic therapy. In limited studies in patients with high-output secretory diarrhoea, including cryptosporidium-related diarrhoea associated with AIDS and in patients with small bowel fistulas, octreotide has been shown to be effective in reducing stool/fistula output. However, well-designed clinical trials are still required to confirm its long term usefulness in these disorders. Similarly, although the use of octreotide in other conditions such as neonatal hypoglycaemia caused by nesidioblastosis, reactive pancreatitis, insulin-dependent diabetes mellitus, postprandial hypotension and the dumping syndrome has provided encouraging preliminary results, more studies are needed to clarify the place of octreotide in their treatment. Overall, octreotide appears to be well tolerated with the most frequently reported reactions being pain at the site of injection and gastrointestinal symptoms such as abdominal cramps, nausea, bloating, flatulence, diarrhoea and steatorrhoea. These adverse effects usually abate with time. Additionally, octreotide, like endogenous somatostatin, may also result in cholelithiasis, presumably by altering fat absorption and possibly by decreasing motility of the gallbladder. Thus, octreotide represents a new departure from traditional therapies in the treatment of various pathophysiological states associated with excessive peptide production and secretion. It offers a significant advantage over existing therapies in the medical management of patients with acromegaly, thyrotrophinomas, the carcinoid syndrome, tumours producing vasoactive intestinal peptide and severe secretory diarrhoea in whom conventional management options have either become exhausted or have provided suboptimal symptomatic relief.