Hormonal regulation of prolactin release by human prolactinoma cells cultured in serum-free conditions

Thyrotropin-releasing hormone (TRH) stimulates the prolactin (PRL) release from normal lactotrophs or tumoral cell line GH3. This effect is not observed in many patients with PRL-secreting tumors. We examined in vitro the PRL response to TRH on cultured human PRL-secreting tumor cells (n = 10) maintained on an extracellular matrix in a minimum medium (DME + insulin, transferrin, selenium). Addition of 10(-8) M TRH to 4 X 10(4) cells produced either no stimulation of PRL release (n = 6) or a mild PRL rise of 32 +/- (SE) 11% (n = 4) when measured 1, 2 and 24 h after TRH addition. When tumor cells were preincubated for 24 h with 5 X 10(-11) M bromocriptine, a 47 +/- 4% inhibition of PRL release was obtained. When TRH (10(-8) M) was added, 24 h after bromocriptine, it produced a 85 +/- 25% increase of PRL release (n = 8). This stimulation of PRL release was evident when measured 1 h after TRH addition and persisted for 48 h. The half maximal stimulatory effect of TRH was 2 X 10(-10) M and the maximal effect was achieved at 10(-9) M TRH. When tumor cells were pretreated with various concentrations of triiodothyronine (T3), the PRL release was inhibited by 50% with 5 X 10(-11) M T3 and by 80% with 10(-9) M T3. Successive addition of TRH (10(-8) M) was unable to stimulate PRL release at any concentration of T3. The addition of 10(-8) M estradiol for up to 16 days either stimulated or had no effect upon the PRL basal release according to the cases. In all cases tested (n = 4), preincubation of the tumor cells with estradiol (10(-8) M) modified the inhibition of PRL release induced by bromocriptine with a half-inhibitory concentration displaced from 3 X 10(-11) M (control) to 3 X 10(-10) M (estradiol). These data demonstrate that the absence of TRH effect observed in some human prolactinomas is not linked to the absence of TRH receptor in such tumor cells. TRH responsiveness is always restored in the presence of dopamine (DA) at appropriate concentration. This TRH/DA interaction seems specific while not observed under T3 inhibition of PRL. Furthermore, estrogens, while presenting a variable stimulatory effect upon basal PRL, antagonize the dopaminergic inhibition of PRL release.     

The combination therapy with bromocriptine and cyproheptadine in patients with acromegaly

The therapeutic efficacy of the combination of cyproheptadine and bromocriptine was studied in 15 patients with active acromegaly showing incomplete GH suppression in response to bromocriptine therapy alone. The mean basal plasma GH was 31.3 +/- 5.5 micrograms/L, and it decreased to 19.0 +/- 3.9 micrograms/L during the single bromocriptine therapy (10 to 20 mg for 2 to 21 months). When cyproheptadine (12 to 16 mg for 8 to 52 months) was added to bromocriptine therapy, plasma GH decreased further (9.4 +/- 3.0 micrograms/L: vs pretreatment, P less than 0.001; vs bromocriptine treatment, P less than 0.005), and GH normalization was obtained in 8 patients. The plasma somatomedin-C levels in these 8 patients (0.3-1.8 U/ml) were within the normal range during the combination therapy. Plasma GH responses to TRH or GHRH were markedly suppressed in 6 patients during the combination therapy compared to pretreatment or during bromocriptine treatment. In addition, a clear reduction in the tumor size was observed in 4 of 7 previously untreated patients during the combination therapy. In conclusion, cyproheptadine has therapeutic efficacy in acromegalic patients who showed incomplete GH suppression in response to treatment with bromocriptine alone. Following the cyproheptadine and bromocriptine combination therapy tumor shrinkage was observed in some patients.     

Evaluation of GH paradoxical responses to TRH and LHRH in acromegalic patients during long-term treatment with octreotide.

In some acromegalics, GH release can be induced by TRH and/or LHRH administration. The pathogenesis of these GH paradoxical responses was supposed to be a somatotroph-reduced sensitivity to somatostatin, somatotrophin release-inhibiting factor (SRIF), or an hypothalamic derangement of the SRIF release. In this study, this hypothesis was investigated by means of GH suppression during chronic therapy with octreotide [Somatostatin analogue (SMS)] in order to evaluate the possible correlation between GH and insulin-like growth factor 1 (IGF-1) normalization and the disappearance of these paradoxical responses in 15 acromegalic patients: 15/15 with a paradoxical GH rise after TRH and 7/15 with a paradoxical GH rise after LHRH. SMS therapy was administered subcutaneously at the dose of 150-450 micrograms/day. During the treatment, GH and IGF-1 levels normalized in 12 patients and were reduced in the remaining 3 others. The GH response to TRH disappeared in 7 patients, while the GH response to LHRH disappeared in 4 patients. chi 2 analysis failed to show any significant correlation between GH and IGF-1 normalization and the disappearance of GH response to TRH and LHRH (chi 2 = 0.00686). No linear correlation existed between GH/IGF-1 decrease and GH peak or area under the curve at any time ('r' values: TRH test, GH -0.47, IGF-1 -0.48; LHRH test, GH -0.50, IGF-1 -0.49). The absence of any significant correlation between GH/IGF-1 normalization and the disappearance of GH paradoxical responses during chronic octreotide administration suggests that other factors apart from SRIF sensitivity are involved in the genesis of these responses.     

The pituitary-thyroid axis in acromegaly

The pituitary-thyroid axis of 12 acromegalic patients was evaluated by measurement of the serum concentrations (total and free) of thyroxine (T4), triiodothyronine (T3) and reverse T3 (rT3) and thyrotropin (TSH), growth hormone (GH) and prolactin (PRL) before and after iv stimulation with thyrotropin releasing hormone (TRH). Using an ultrasensitive method of TSH measurement (IRMA) basal serum TSH levels of the patients (0.76, 0.07-1.90 mIU/l) were found slightly, but significantly (P less than 0.01), lower than in 40 healthy controls (1.40, 0.41-2.50 mIU/l). The total T4 levels (TT4) were also reduced (84, 69-106 nmol/l vs 100, 72-156 nmol/l, P less than 0.01) and significantly correlated (P less than 0.02, R = 0.69) to the TSH response to TRH, suggesting a slight central hypothyroidism. The acromegalics had, however, normal serum levels of TT3 (1.79, 1.23-2.52 nmol/l vs 1.74, 0.78-2.84 nmol/l, P greater than 0.10), but significantly decreased levels of TrT3 (0.173, 0.077-0.430 nmol/l vs 0.368, 0.154-0.584 nmol/l, P less than 0.01) compared to the controls. The serum concentration of the free iodothyronines (FT4, FT3, FrT3) showed similar differences between acromegalics and normal controls. All the acromegalics showed a rise of serum TSH, GH and PRL after TRH. Positive correlation (P less than 0.05, R = 0.59) was found between the TSH and GH responses, but not between these two parameters and the PRL response to TRH. These findings may be explained by the existence of a central suppression of the TSH and GH secretion in acromegalic subjects, possibly exerted by somatostatin. Euthyroidism might be maintained by an increased extrathyroidal conversion of T4 to T3.     

Improvement of diabetes after treatment with somatostatin analogue SMS 201-995 in an acromegalic patient

The beneficial effects of long acting somatostatin analogue SMS 201-995 in an acromegalic patient affected by severe diabetes mellitus are reported. Neither human insulin alone nor human insulin plus bromocriptine allowed satisfactory metabolic control though, with the latter treatment, virtually normal plasma GH levels were reached. Conversely, addition of SMS 201-995 to insulin treatment led to normalization of blood glucose. This result was obtained with a dose of SMS 201-995 of 400 micrograms/day and only after 3 weeks of therapy.     

A retrospective hormonal and immunohistochemical evaluation of 47 acromegalic patients: prognostic value of preoperative plasma prolactin.

This study was performed to investigate the correlations between preoperative prolactin (PRL) plasma values, immunohistochemical picture and the clinical course in growth hormone (GH) secreting pituitary adenomas. In 47 patients (19 males and 28 females; mean age 40 years; range 13 - 70 years), we measured GH, IGF-1 and prolactin plasma values both before and after transsphenoidal surgery, and basal IGF-1 and GH after an oral glucose tolerance test (OGTT) during four years of follow-up. We considered those patients as "controlled" who presented an undetectable growth hormone after OGTT (GH < 1 microg/l), IGF-I plasma values in the normal range, matched for age and sex, and no clinical activity or neuroradiological recurrence after a four-year follow-up. We considered patients as "poorly controlled" who still showed elevated GH and IGF-I plasma levels, uninhibited GH after OGTT (GH > 1 microg/l), presence of clinical activity and/or radiological signs of adenoma recurrence, even if a reduction of tumor size had been demonstrated. RESULTS: Controlled patients (n = 22) exhibited mean preoperative PRL levels (+/- SEM) lower than the group of poorly controlled (n = 25) ones (21.40 +/- 5.51 vs. 38.44 +/- 5.16 microg/l; p < 0.03). From 3 to 12 months after surgery, postoperative PRL levels were also lower in the controlled patients compared to the poorly controlled ones (8.31 +/- 1.20 vs. 25.32 +/- 3.20 microg/l; p < 0.0001). Eighty percent (20/25) of poorly controlled patients showed both PRL and GH positivity after immunostaining. Only 3/22 (13.6 %) of controlled patients showed the same double positivity. In conclusion, preoperative hyperprolactinemia identifies a group of acromegalic patients at elevated risk of disease persistence after surgery. We hypothesize that most of these high-risk patients may have more aggressive mixed GH-PRL secreting adenomas.     

Long-term bromocriptine therapy and predictive tests in acromegaly

The value of predictive tests in bromocriptine therapy and the effects of long-term bromocriptine therapy were investigated in acromegalic patients. In 72 acromegalic patients, there was a tendency for patients with a plasma GH response to TRH or with an elevated basal plasma PRL level, but without a plasma GH response to LHRH, to have a plasma GH response to bromocriptine, though statistical analysis did not reveal a significant difference. Acute and chronic effects of bromocriptine were significantly interrelated, while the chronic effect of bromocriptine and abnormal plasma GH response to TRH or elevated plasma PRL levels were not, in 18 acromegalic patients. These results suggest that the acute bromocriptine test is a better predictor than the TRH test and plasma PRL levels for evaluating the effects of chronic bromocriptine therapy. To maintain the low plasma GH levels, increasing doses of bromocriptine were needed in most patients, and failure to control the elevated GH level despite increasing doses was observed in 2 of 18 patients.     

Prolactin and growth hormone synthesis and thymidine incorporation in dissociated rat pituitary tumor cells

The effect of in vivo diethylstilbestrol (DES) treatment on the MtT/W15 transplantable pituitary tumor was examined in dissociated pituitary cells by measuring the rate of incorporation of [3H]thymidine into DNA and the synthesis of prolactin (PRL) and growth hormone (GH) as assessed by the rate of incorporation of [3H]leucine. MtT/W15 transplantable pituitary tumors from rats treated for 3 weeks with DES showed significant reduction in the extent of [3H]thymidine incorporation compared with tumor cells from untreated rats (2231 +/- 182 vs 172 +/- 17 dpm/10(5) cells; n = 3). In addition, tumor cells from DES-treated rats showed a significant increase in GH synthesis compared with tumor cells from untreated rats. In contrast to these findings, dissociated pituitary cells from non-tumor-bearing rats given 10 mg DES in Silastic tubing for 3 weeks showed a three-fold increase in PRL synthesis compared to cells from untreated control rats (29.3 +/- 1.5 vs 10.0 +/- 0.9% of total radioactivity in gel; n = 3. There was also a four-fold increase in the rate of [3H]thymidine incorporation after DES-treatment in non-tumor-bearing rats (695 +/- 114 vs 178 +/- 13.9 dpm/10(5) cells; n = 3). These results indicate that DES inhibits MtT/W15 pituitary tumor cell proliferation, while stimulating synthesis of GH.     

Treatment of acromegaly with long acting somatostatin analogue SMS 201-995

Ten acromegalic patients were treated with the somatostatin analogue SMS 201-995 (SMS) for 3-38 weeks in various doses and by different administration routines (thrice daily or multiple sc injection). Plasma GH daily profiles, plasma IGF-I, urinary GH, serum TSH, IRI and fasting blood glucose (FBG) concentrations were measured before and during SMS treatment. Plasma GH rapidly decreased within one hour in all patients and was suppressed for at least 4 h after a 50 micrograms sc injection of SMS in 8 patients. Multiple injections of 300-600 micrograms/day SMS (25-50 micrograms X 12) suppressed GH throughout the day. Plasma IGF-I was completely normalized in 4 patients, and, in all but one of the others, decreased markedly. Urinary GH decreased within the first week of treatment in all patients and normalization was obtained in 3 patients. Shrinkage of the pituitary tumor, as determined by CT or MRI, was observed in 7 of 9 patients. Other clinical improvements, such as diminution or complete disappearance of swelling of soft tissues, excessive perspiration, and headache, were observed in 7 of 8 patients. Changes in serum TSH, IRI and FBG were seen in 3-4 patients, but without any apparent clinical problems. In conclusion, SMS is a useful clinical tool for treatment of acromegaly, and a multiple sc injection method seems to be preferable.     

Oral thyrotropin-releasing hormone (TRH) test in acromegaly

The effects of 40 mg oral and 200 microgram intravenous TRH were studied in patients with active acromegaly. Administration of oral TRH to each of 14 acromegalics resulted in more pronounced TSH response in all patients and more pronounced response of triiodothyronine in most of them (delta max TSh after oral TRh 36.4 +/- 10.0 (SEM) mU/l vs. delta max TSH after i.v. TRH 7.7 +/- 1.5 mU/l, P less than 0.05; delta max T3 after oral TRH 0.88 +/- 0.24 nmol/vs. delta max T3 after i.v. TRH 0.23 +/- 0.06 nmol/l, P less than 0.05). Oral TRH elicited unimpaired TSH response even in those acromegalics where the TSH response to i.v. TRH was absent or blunted. In contrast to TSH stimulation, oral TRH did not elicit positive paradoxical growth hormone response in any of 8 patients with absent stimulation after i.v. TRH. In 7 growth hormone responders to TRH stimulation the oral TRH-induced growth hormone response was insignificantly lower than that after i.v. TRH (delta max GH after oral TRH 65.4 +/- 28.1 microgram/l vs. delta max GH after i.v. TRH 87.7 +/- 25.6 microgram/l, P greater than 0.05). In 7 acromegalics 200 microgram i.v. TRH represented a stronger stimulus for prolactin release than 40 mg oral TRH (delta max PRL after i.v. TRH 19.6 +/- 3.22 microgram/, delta max PRL after oral TRH 11.1 +/- 2.02 microgram/, P less than 0.05). Conclusion: In acromegalics 40 mg oral TRH stimulation is useful in the evaluation of the function of pituitary thyrotrophs because it shows more pronounced effect than 200 microgram TRH intravenously. No advantage of oral TRH stimulation was seen in the assessment of prolactin stimulation and paradoxical growth hormone responses.     

Comparison between a slow-release oral preparation of bromocriptine and regular bromocriptine in patients with hyperprolactinemia: a double blind, double dummy study.

The efficacy and tolerability of a slow-release preparation of bromocriptine (Parlodel SRO) were compared to those of conventional bromocriptine (Parlodel R) in a double blind, double dummy study of 12 hyperprolactinemic women (plasma PRL 81.3 +/- 4.73, ng/ml mean +/- SEM). For 2 weeks, the patients received 2.5 mg b.i.d. Parlodel R or 5 mg once daily Parlodel SRO; for the following 2 weeks, the dose of the drugs was doubled. The patients were then treated, in an open study, with 2.5-10 mg daily Parlodel SRO for 6 months. Both preparations caused a prompt and sharp PRL fall. Hormone levels remained inhibited over the whole month of observation with both preparations. Daily PRL profiles were very close with either drug although morning PRl levels were slightly higher during Parlodel SRO than during Parlodel R administration. Doubling the doses of the two drugs did not result in further significant lowering of PRL values. During the 6-month study with Parlodel SRO, plasma PRL further decreased and normalized in 11 of 12 patients. Clinical improvement occurred in the majority of cases. Tolerability of Parlodel SRO appeared to be better, though without statistically significant differences, than that of Parlodel R. Side effects were less important with the former compound in their number, severity and duration. In conclusion, thanks to its favourable pharmacological profile, Parlodel SRO appears to be a valuable alternative to regular bromocriptine in the management of hyperprolactinemia.     

Experience of a six-month treatment with sandostatin at increasing doses in acromegaly

The French Sandostatin/Acromegaly Study Group performed a multicentric, prospective, open-label trial of incremental doses with the aim of obtaining the best antisecretory effect. Forty-two patients (24 women, 18 men) aged 22-71 years were involved, either after unsuccessful surgery and/or radiotherapy (30 patients), or as primary treatment (12 patients). Doses were increased from 3 x 100 to 3 x 500 micrograms/day, according to the results of hormonal investigations (GH profiles and Sm-C) performed each month and for each dose, and tolerability. Four patients dropped out because of major digestive troubles. Recurrent pain at the injection site and minor gastrointestinal disorders were noted in some patients. Asymptomatic gallstones appeared in 4 patients. Carbohydrate tolerance and insulin secretion (determined by diurnal plasma glucose and insulin profiles) were not significantly altered by the various SMS doses. Clinical improvement was determined by the scoring of the symptoms. Mean plasma GH concentrations were significantly reduced for each SMS dose, compared to pretreatment values. Fifteen patients obtained 75% of GH values less than or equal to 2 micrograms/l. In 9 patients the highest dose failed to bring GH below 10 micrograms/l. Sm-C normalized in 17/31 patients. After 6 months of treatment a tumor reduction of 20-50% was found in 7 patients and greater than 50% in 5 patients. We conclude that (1) the tolerability of SMS is compatible with long-term treatments; (2) clinical improvement and biological criteria of efficacy are obtained in 3/4 acromegalic patients treated by SMS, and that (3) some patients are resistant to SMS and the increase in the dose does not improve the result.     

Suppression of growth hormone and somatomedin C by long-acting somatostatin analog SMS 201-995 in type I diabetes mellitus

The effect of a new long-acting somatostatin analog SMS 201-995 (SMS) on hormonal mechanisms controlling the glucose metabolism was tested in 8 type I diabetics over a 3-day period. In addition to dietary measures and conventional insulin therapy, the patients received a subcutaneous dose of 50 micrograms SMS three times daily for 3 days. Serum growth hormone (GH) was measured at various intervals throughout the investigational period. Glucagon, somatomedin C (SM-C), triiodothyronine, thyroxine, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were also determined before and at the end of the therapy with SMS. Basal GH and plasma SM-C had decreased significantly (p less than 0.05 and p less than 0.01, respectively) by the 3rd day. In all cases the insulin requirements could be reduced (mean 28%) without deterioration of the metabolic control. Moreover, blood glucose profiles showed a tendency to lower postprandial peaks after SMS treatment. Glucagon, triiodothyronine, thyroxine, LH, FSH and PRL showed no significant changes. No side effects or alterations in laboratory chemistries were recorded. Dampening of glucose oscillations and counterregulatory mechanisms, and reduction of insulin dosage by SMS may enable a better control of unstable diabetes. Its slow plasma clearance and long action compared to the native peptide will warrant the use of this analog as a additive to standard diabetes therapy in more prolonged trials.     

Effect of opiates on growth hormone secretion in acromegaly.

Morphine at doses of 5 mg and 10 mg does not stimulate growth hormone (GH) secretion in normal subjects, and its effect on GH secretion in acromegaly is not widely documented. We investigated the effect of 15 mg intravenous morphine on growth hormone in patients with active acromegaly compared to normal subjects (7 acromegalics and 5 controls). Their mean (+/- SEM) age was 30.5 +/- 7.6 years and 29.5 +/- 0.5 years, respectively. Basal and peak response of growth hormone after morphine was measured with simultaneous assay of cortisol to exclude the effect of stress. Mean (+/- SEM) basal growth hormone was 103.16 +/- 28.04 ng/ml in acromegalics compared to 4.51 +/- 1.43 ng/ml in controls. Morphine caused an elevation of growth hormone in both acromegalics and normal subjects (p < 0.05). However, the Delta (peak minus basal) response of growth hormone was comparable between the two groups. A concurrent fall in cortisol was noted after morphine in both the groups, excluding the effect of stress on growth hormone. We conclude that higher doses (15 mg) of morphine are required to stimulate GH secretion in normal subjects, and that opioids exert a positive modulating effect on growth hormone secretion in patients with active acromegaly suggesting partial autonomy of the pituitary tumor.     

Results of a two-year treatment with slow release lanreotide in acromegaly.

In this open sequential study we evaluated the long-term effectiveness and tolerability of the i.m. administration of slow release lanreotide 30 mg (SRL) in 18 acromegalics (7 M/11 F, age 50.9+/-12.7 yr). Baseline mean GH and IGF-1 levels were 15.8+/-6.6 ng/ml and 702+/-74 ng/ml, respectively. Four hours, 1, 7, and 14 days after SRL, mean GH levels were 8.9+/-5.9 (p < 0.005), 11.4+/-6.9 (p < 0.05), 9.1+/-4.5 (p < 0.05), and 9.1+/-4.1 ng/ml (p < 0.05), respectively; and the IGF-1 values at 1, 7, and 14 days were 624+/-77 (p < 0.05), 555+/-83 (p < 0.001), and 467+/-58 ng/ml (p < 0.0001), respectively. Four hours after SRL administration GH was < 2.5 ng/ml in 11 patients and decreased 85% of the basal value, without normalizing, in another case. In the following 2 weeks, 7 and 2 patients maintained GH < 2.5 ng/ ml or < 50% of baseline; 3 and 2 of them attained IGF-1 values in the normal range or < 50% of basal levels. A patient developed acute pancreatitis after the injection of the drug and therefore stopped the treatment. Another patient did not continue SRL, and she was turned on octreotide, s.c. administered (OCT), because only the latter treatment ameliorated significantly the headache. In 16/18 patients the treatment was continued until the 24th month. SRL was administered every 14 days until the 24th month in 3 cases, whereas in 13 patients the dose schedule was increased every 10 days since the 7th month because they did not normalize serum GH and IGF-1 levels. In these 16 patients baseline GH and IGF-1 levels were 10.0+/-2.5 ng/ml and 671+/-75 ng/ml, respectively. At the 1st, 3rd, and 6th month of treatment mean GH levels fell to 5.4+/-1.4 (p < 0.05), 5.3+/-1.8 (p < 0.05), and 5.0+/-1.6 (p < 0.05) ng/ml, respectively; and IGF-1 declined to 511+/-87 (p < 0.005), 565+/-85 (p < 0.05), and 525+/-94 (p < 0.01) ng/ml, respectively. Throughout the first semester GH was < 2.5 ng/ml in 5 patients and decreased > 50% in another three. IGF-1 levels normalized in 3/5. Throughout the following 18 months of treatment, mean GH (3.4+/-1.0 ng/ml) and IGF-1 (413+/-75 ng/ml) values decreased significantly in comparison with both the baseline concentrations (GH p < 0.01, IGF-1 p < 0.001) and the levels measured during the 1st semester of treatment (GH p < 0.05, IGF-1 p < 0.001). GH remained < 2.5 ng/ml in 11 patients, and in 8/11 cases IGF-1 fell in the normal range. Serum GH and IGF-1 levels decreased by more than 50% of baseline levels in 2 other cases. At MRI, pituitary adenoma was no longer evident in one patient previously treated with OCT and significantly decreased in another patient previously treated with surgery plus radiotherapy, as well as in a patient previously untreated. During treatment the percentage of patients complaining of headache and fatigue decreased significantly (chi2, p < 0.05 and p < 0.0005, respectively). Overall, the headache (p < 0.005), arthralgia (p < 0.05), and paresthesia (p < 0.01) ameliorated significantly. Ultrasound scan showed gallbladder sludge or sand-like stones in 5/11 patients. This study, which is one of the longest surveys on a relatively large series of acromegalics treated with SRL, confirms the long-term effectiveness of this drug for the treatment of patients with active acromegaly. SRL decreases significantly GH and IGF-1 in most cases and induces the shrinkage of the pituitary tumor in some patients previously either untreated or both treated for acromegaly. SRL improves significantly clinical symptoms and it is well tolerated.     

Prolactinomas and resistance to dopamine agonists.

Among 288 patients with prolactinoma (aged 12-62 years; 242 women), 27 were diagnosed as resistant to bromocriptine as their plasma prolactin (PRL) levels remained elevated despite long-term (3 months or more) treatment at high doses (> or = 15 mg daily). These 18 women and 9 men, aged 29 +/- 9 years (mean +/- SD, range 13-50), followed-up for 8 +/- 4 years, had microadenomas (n = 6) or macroadenomas. They were treated by dopamine agonists alone (n = 6) or associated with surgical or radiation therapy. In 8 cases repetitive surgical treatments were necessary. Among the 24 patients who were treated with the nonergot dopamine agonist CV 205-502 after unsuccessful bromocriptine treatment, half of them (9 women, 3 men) resumed normal PRL levels on doses ranging from 0.15 to 0.45 mg/day. Despite daily doses of CV 205-502 from 0.3 to 0.525 mg, the remaining patients were not normalized by this drug which did not prevent tumor growth in 4 of them. Two patients died from invasive cerebral extensions of their tumor and a third had vertebral metastases with positive anti-PRL immunostaining. It is concluded that bromocriptine-resistant prolactinomas represent the most severe aspect of this disease and that a more powerful dopamine agonist like CV 205-502 is effective in only a fraction of these patients.     

In vitro short-term effects of SMS 201-995, bromocriptine and TRH on growth hormone cell morphology from human pituitary adenomas

This study reports, by immunocytochemistry, ultrastructure and morphometry, the in vitro effects of SMS 201-995 (10 nM), bromocriptine (1 microM) and TRH (10 microM) on the morphology of cells from two acromegalic patient adenomas containing immunoreactive growth hormone (GH). By electron microscopy, one tumor presented numerous large secretory granules (densely granulated growth hormone cell adenoma) while they were scarce and small in the other (sparsely granulated growth hormone cell adenoma); fibrous bodies could be seen in the specimen and in vitro. In the sparsely granulated growth hormone cell adenoma, TRH produced an increase in endoplasmic reticulum surface density compared to the other cultures. Bromocriptine increased the number and decreased the secretory granule diameters, while SMS 201-995 produced no significant changes in the same time. In the densely granulated growth hormone cell adenoma, the three substances increased the number of granules. TRH increased the mitochondrial volume density and endoplasmic reticulum surface density (with respect to the other cultures). SMS 201-995 decreased the mitochondrial and lysosome volume densities and endoplasmic reticulum surface density. We conclude that 1) TRH produces in cultured cells of both adenoma types an increase in cellular activity. 2) In cultured sparsely granulated growth hormone adenoma cells, bromocriptine has a stronger inhibitory effect than SMS 201-995. In cultured densely granulated growth hormone cells adenoma, bromocriptine has smaller inhibitory effect than SMS 201-995.     

Serum thyrotropin response to combined arginine and thyrotropin-releasing hormone administration provides evidence for an altered somatostatinergic tone in acromegaly.

The aim of this study was to evaluate plasma thyrotropin (TSH), prolactin (PRL) and growth hormone (GH) responses to the TSH-releasing hormone (TRH) test and to a combined arginine-TRH test (ATT-TRH) in 10 normal subjects and in 15 acromegalic patients. In controls, TSH responsiveness to TRH was enhanced by ATT (p less than 0.001). When considering the 15 acromegalic patients as a whole, no significant difference in TSH responses was detected during the two tests. However, patients without suppression of plasma GH levels after oral glucose load showed an increased TSH responsiveness to the ATT-TRH test if compared to TRH alone (p less than 0.025), while patients with partial suppression of plasma GH levels after glucose ingestion showed a decreased TSH responsiveness to ATT-TRH (p less than 0.05). No difference was recorded in PRL and GH responses, evaluated as area under the curve, during TRH or ATT-TRH tests in controls and in acromegalics. In conclusion, (1) normal subjects have an enhanced TSH response to the ATT-TRH test and (2) acromegalic patients without suppression of GH levels after oral glucose load show a TSH responsiveness to the ATT-TRH test similar to that of controls, while acromegalics with partial GH suppression after oral glucose load have a decreased TSH responsiveness to the ATT-TRH test. These data suggest that acromegaly is a heterogeneous disease as far as the somatostatinergic tone is concerned.     

Isolation and characterization of rat-mouse somatic cell hybrids secreting growth hormone and prolactin

Interspecific somatic cell hybrid clones have been isolated and characterized in order to study growth hormone (GH) and prolactin (PRL) gene expression. Rat pituitary tumor cells (GH3, 69 chromosomes) secreting rat GH and PRL were grown for 48 h together with nonhormone secreting, aminopterin-sensitive murine fibroblast cells (LMTK-, 55 chromosomes) and fused using polyethylene glycol. Resultant heterokaryons were selected in hypoxanthine-aminopterin-thymidine (HAT) medium and cloned. Five clones produced rat GH and PRL. Hormone-producing hybrids morphologically resembled the mouse parent fibroblast. Hybrids grew in monolayers and contained 80-142 chromosomes, and marker chromosomes for both rat (small submetacentric) and mouse (bi-armed and large true metacentric) were identified. The interspecific nature of the hybrids was further confirmed by the presence of both rat and mouse adenosine deaminase and superoxide dismutase isozymes. Using specific antisera and indirect immunoperoxidase staining, both hybrid clones and GH3 rat parental cells stained positively for rat GH and PRL, while the murine fibroblast parental cells were negative. Hormone production by the hybrids has been sustained for over twenty subcultures; secretion rates were initially 150 ng PRL and 321 ng GH/10(6) cells/24 h and are currently 100 ng PRL and 90 ng GH/10(6) cells/24 h. Parental GH3 rat cells secreted 720 ng PRL and 660 ng GH/10(6) cells/24 h. Exposure of hybrids to KCl (50 mM) resulted in acute stimulation of rat PRL, but not rat GH release, and long-term incubation with thyrotropin-releasing hormone (TRH, 80 nM) stimulated PRL secretion. Hormone-dependent modulation of PRL secretion was transferred to the hybrid cell thus enabling the model to be used in studying regulation of PRL gene expression.