SMS 201-995 and thyroid function in acromegaly: acute, intermediate and long-term effects

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.

Effect of 4 weeks of octreotide treatment on prolactin, thyroid stimulating hormone and thyroid hormones in acromegalic patients. A double blind placebo-controlled cross-over study

We aimed to test the hypothesis, that octreotide has a suppressive effect on unstimulated and TRH-stimulated PRL levels in both normo- and hyperprolactinaemic acromegalic patients, and besides to evaluate the effect of octreotide on unstimulated TSH and thyroid hormones. The present study is a doubleblind placebo-controlled cross-over trial; the 12 acromegalic patients were treated with octreotide or placebo (300 micrograms/d) for 4 weeks separated by a 12 weeks washout period. Before and after each 4 weeks period a TRH-test (200 micrograms iv) was performed and serum GH and PRL levels were determined. Serum TSH and thyroid hormones were determined after 0, 2, 3, and 4 weeks. In the whole group unstimulated PRL levels were 18 micrograms/l +/- 5 before and 7 micrograms/l +/- 1 during octreotide treatment (p < 0.01). The PRL lowering effect of octreotide was significantly more pronounced in hyperprolactinemic patients compared to normoprolactinaemic patients (p < 0.05). Patients with the highest pretreatment PRL levels had the most pronounced percentage suppression of unstimulated PRL levels during octreotide treatment. Eight out of 12 patients had a TRH-stimulated PRL response > or = 100%, both during placebo and octreotide treatment, but in the group as a whole maximal TRH-stimulated PRL levels were suppressed during octreotide treatment, PRL levels were 50 micrograms/l +/- 20 before and 18 micrograms/l +/- 3 during octreotide treatment (p < 0.05). Unstimulated GH levels were 48 mU/l +/- 15 before and 13 mU/l +/- 2 during octreotide treatment (p < 0.01). Serum total T3 was significantly reduced during octreotide treatment (p < 0.05); serum TSH, total T4 or free T4 index were not significantly changed during treatment. We conclude that patients with acromegaly and hyperprolactinemia will normalize PRL levels during 4 weeks of octreotide treatment and octreotide will reduce total T3 levels in acromegalic patients.

Continuous versus intermittent subcutaneous infusion of octreotide in the treatment of acromegaly

This review evaluates the efficacy, tolerability, and safety of continuous subcutaneous infusion (CSI) relative to intermittent subcutaneous injection (ISI) of the somatostatin analog, octreotide in the treatment of acromegaly. Data was extracted from five clinical series using CSI octreotide in acromegaly, six reports comparing CSI to ISI, and three studies comparing pulsatile subcutaneous infusion (PSI) to ISI. Effects of each drug regimen on the control of growth hormone (GH), insulin-like growth factor (IGF-1), clinical symptomatology, pituitary tumor size, and adverse effects were evaluated. Normalization of serum GH or IGF-1 levels, as well as improvement in clinical symptoms was reported in the majority of the patients studied. Cases in which pituitary adenomas decreased in size were also documented during the study period. When the effects of CSI were compared with ISI, a more pronounced control of GH and IGF-1 was observed. In addition, diurnal GH fluctuation during CSI was significantly reduced relative to ISI in two reports. Moreover, in two patients, CSI achieved similar clinical and biochemical effects at lower doses than when the drug was given by ISI. Finally, adverse effects with CSI may be less severe than with ISI. Continuous subcutaneous infusion of octreotide produced biochemical improvement in 67 of the 88 patients reviewed. When compared with ISI, CSI induced more pronounced biochemical control, often with less fluctuation in GH and IGF-1 levels. Because of a lack of data, definite conclusions regarding the differences between regimens on clinical symptomatology and tolerability could not be discerned. A large prospective, long-term randomized crossover study is recommended to make these determinations.

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.

Long-term efficacy and tolerability of octreotide treatment in acromegaly

Twenty-five acromegalic patients were studied during 6 years of treatment with octreotide, with a particular focus on the following parameters: (1) Administration schedule: in 10 patients, continuous subcutaneous (SC) octreotide infusion was compared with injections of octreotide at three dose levels (100, 250, and 1,500 micrograms/24 h) and was found to induce a greater and less-fluctuating 24-hour growth hormone (GH) suppression. (2) Carbohydrate tolerance: average 24-hour blood glucose levels were unaffected by octreotide, regardless of administration schedule. Oral carbohydrate tolerance and intravenous (IV) glucose tolerance were unaffected by continuous octreotide infusion. However, octreotide injection given shortly before the tests reduced carbohydrate tolerance. (3) Thyroid function: octreotide and somatostatin acutely reduce the response of thyroid-stimulating hormone (TSH) to thyrotropin-releasing hormone (TRH). After a few days of treatment, it was demonstrated that octreotide slightly inhibits iodothyronine deiodination and induces a transient reduction in serum triiodothyronine (T3), rapidly compensated for by a persistent slight elevation of serum TSH. (4) Fat absorption was estimated as 24-hour fecal fat content and found to be in the same high-normal range before and after octreotide treatment. Vitamin K and D absorption were unaffected by octreotide. The incidence of gallstone formation was not greater than in the general Danish population, possibly due to the schedule used for octreotide injections. (5) Foot volume was regularly estimated and found to decrease with time, on average by 12% during the first 18 months.(ABSTRACT TRUNCATED AT 250 WORDS)