K. Mashiter

SECRETION OF LH, FSH AND PRL SHOWN BY CELL CULTURE AND IMMUNOCYTOCHEMISTRY OF HUMAN FUNCTIONLESS PITUITARY ADENOMAS

Hormone secretion by ten functionless human pituitary adenomas in cell culture has been measured, and compared with tissue immunocytochemistry and electron microscopy, as well as results with a normal pituitary. Patients presented following routine x‐ray and had no clinical or biochemical endocrine abnormality apart from one male with raised serum FSH and PRL, normal LH, and low testosterone. Of the ten adenomas, nine secreted both LH and FSH in cell culture and five of these also secreted PRL, one did not secrete any anterior pituitary hormones (ACTH was not measured). No GH or TSH was detectable in the cultures of the nine LH/FSH secretors excluding the possibility of contamination by normal anterior pituitary. The normal pituitary cells secreted all anterior pituitary hormones; the amounts of FSH/LH being comparable with those of the adenomas. Immunostaining confirmed the cell culture results and showed the adenoma FSH/LH cells to be scattered singly or in small groups of two to five cells with both hormones usually being in the same cell. PRL where found was in separate cells. Hormone granules were small (50–160 nm), round or irregular and scattered in the cytoplasm of rounded cells of low secretory activity. The negatively staining cells were not different ultrastructurally to those staining positively. It is concluded that a significant proportion of functionless pituitary adenomas have detectable low levels of LH/FSH secretion often accompanied by PRL when examined by cell culture or immunocytochemistry. Although these adenomas were endocrinologically quiescent activity could have been masked because of post‐menopausal secretion and one male probably had an FSH‐secreting adenoma.

Bromocriptine treatment of acromegaly

Bromocriptine at a dose of 7.5-30 mg/day was given to 12 acromegalics for 6 mo. Mean serum growth hormone (GH) levels during a glucose tolerance test (GTT) were significantly lowered by the drug. In four patients the serum GH response during a GTT was suppressed to normal (i.e. less than or equal to 5 mlU/liter). If bromocriptine had not brought the serum GH response to a GTT to normal at a dose of 20 mg/day, this effect was not achieved by raising the dose to 30 mg/day. Bromocriptine was effective for the duration of treatment. On discontinuing therapy there was an increase in serum GH levels. No obvious clinical changes in the acromegalic features were noted. One patient with impaired glucose tolerance and one with established diabetes had normal glucose tolerance while on bromocriptine and another two patients with impaired glucose tolerance showed no obvious changes while on the drug. Side effects were minor. X-rays of the pituitary fossa before starting and at the end of treatment showed no significant change. We conclude that although bromocriptine is the most promising form of medical treatment for acromegaly to date, it is fully effective only in a minority of patients.

GONADOTROPHIN AND ALPHA SUBUNIT SECRETION BY HUMAN ‘FUNCTIONLESS’ PITUITARY ADENOMAS IN CELL CULTURE: LONG TERM EFFECTS OF LUTEINIZING HORMONE RELEASING HORMONE AND THYROTROPHIN RELEASING HORMONE

The long‐term effects of LHRH and TRH on gonadotrophin alpha subunit, FSH and LH secretion by cell cultures of four human chromophobic pituitary tumours have been examined. The tumours derived from one male and three female patients who presented because of visual disturbance but had no evident endocrine symptoms. Subsequent serum hormone analysis showed the FSH to be high in the male but low or normal in the post‐menopausal females whereas LH levels were low in all patients. In culture, basal hormone secretion could be maintained for periods up to 63 d. All tumours secreted alpha subunit and FSH, but much lower amounts of LH. Addition of LHRH or TRH for a period of 12 to 41 d showed that alpha subunit, FSH and LH secretion were stimulated by LHRH from one tumour, by LHRH and TRH from two tumours. There was always a rapid decline in the LH secretion. The tumour which secreted FSH predominantly was stimulated by TRH. We conclude that human pituitary ‘functionless’ adenomas can secrete gonadotrophin alpha subunit and FSH in vitro and that secretion can be stimulated during long term releasing hormone experiments. LH secretion, however, cannot be maintained.

BROMOCRIPTINE SUPPRESSES ACTH SECRETION FROM HUMAN PITUITARY TUMOUR CELLS IN CULTURE BY A DOPAMINERGIC MECHANISM

Bromocriptine (0·13–13 μM) significantly inhibited ACTH secretion in a dose‐dependent manner when added to cell cultures of a human corticotrophic adenoma for 24 h. Haloperidol (13 μM), but not serotonin (13 μM), blocked this inhibition but had no significant effect when added alone. In addition, dopamine (10 μM) reduced ACTH secretion during a 4‐h incubation, whereas serotonin (0·01–10 μM) was ineffective. An ectopic ACTH secreting lung carcinoid was non‐responsive to doses of bromocriptine up to 13 μM. These results demonstrate a direct suppressive action of bromocriptine on a human pituitary corticotrophic adenoma through dopaminergic rather than sero‐toninergic mechanisms.

HYPERTHYROIDISM DUE TO A TSH SECRETING PITUITARY ADENOMA: CASE REPORT, TREATMENT AND EVIDENCE FOR ADENOMA TSH BY MORPHOLOGICAL AND CELL CULTURE STUDIES

A 36‐year‐old woman with recurrent hyperthyroidism, inappropriately elevated serum TSH, and an 8 mm pituitary microadenoma is described. Transsphenoidal adenomectomy rapidly reduced serum TSH to normal and restored the euthyroid state with retention of other anterior pituitary functions. Tissue removed at operation was examined by light and electron microscopy and cell culture. The tissue was neoplastic, composed of irregular often elongated cells which immunostrained positively only with antisera to β‐TSH. The cells contained small granules (100–170 nm) usually along the cell membrane. In cell culture TSH alone was secreted and the rate of secretion declined with time. We conclude that the patient had a TSH secreting microadenoma as a cause of her hyperthyroidism.

Production and storage of [125I] thyroxine and [125I] triiodothyronine of high specific activity

High specific activity [125-I] triiodothyronine and [125-I] thyroxine have been produced regularly by the chloramine T radioiodination method. Simultaneous production of [125-I] triiodothyronine and [125-I] thyroxine is usual when diiodothyronine or triiodothyronine are employed as the starting materials. Specific activities reached vary with the starting compound (diiodothyronine, triiodothyronine, thyroxine) used, as both substitution and, less readily, exchange of iodine atoms take place. Starting with diiodothyronine specific activities of approximately 2400 and 5200 Ci/g were achieved for [125-I]triidothyronine and [125I] thyroxine, respectively, and, similarly, specific activities of approximately 1200 and 4000 Ci/g for [125I] triiodothyronine and [125I]-thyroxine, respectively, were reached when triiodothyronine was the starting material. [125-I] Triiodoacetic acid and [125I] tetraiodoacetic acid have been produced in the same way from triiodoacetic acid. By column chromatography on Sephadex G-25 (fine), eluting with alkaline phosphate buffer, good separation of the radioiodinated products has been readily achieved. Studies on the stability of the radioiodinated hormones showed that 50% methanol, ethanol, propanol and propylene glycol were all equivalent as preserving agents and, further, that the stability of the radioiodinated hormones was linearly related to the concentration of these preserving agents.

EFFECT OF PANCREATIC GROWTH HORMONE RELEASING FACTORS ON GH SECRETION BY HUMAN SOMATOTROPHIC PITUITARY TUMOURS IN CELL CULTURE

Human pancreatic growth hormone releasing factors (hpGRF(1–40) and hpGRF(1–44)) significantly stimulated GH secretion when added to cell cultures of human somatotrophic pituitary tumours for 2 h. There was little difference in potency between the two peptides, and the response of different tumours varied, ranging from 30% to 500% increases in GH secretion over control levels. This stimulatory effect was blocked by somatostatin (SRIF) and bromocriptine. The suppressive effect of bromocriptine, but not of SRIF, was overcome by high doses of hpGRF(1–44). TRH stimulated GH secretion by one of three somatotrophic tumours in cell culture, and it was found to potentiate the stimulatory effects of hpGRF(1–44). These results demonstrate that hpGRFs increase serum GH levels in man by a direct action at the pituitary somatotroph level.

TREATMENT OF CUSHING'S DISEASE IN JUVENILES WITH INTERSTITIAL PITUITARY IRRADIATION

Nine juvenile patients (five boys and four girls aged 10–18) with Cushings disease were treated with pituitary implantation of 198 Au and/or 90Y. No patient had any surgical complication from the procedure. At the latest assessment, 3 months to 17 years after operation, Cushings disease was in remission in all the patients; the response time following operation was a few days to 3 months. Radiology of the pituitary fossa at time of pituitary implantation was normal in all patients and remains so. The final height in six patients is 149–172 cm (59–67.5 inches) and three patients who continue to grow have increased by 13, 6 and 3 cm since implantation. Only one patient required full pituitary hormone replacement therapy, and he had been previously treated by external irradiation, and one other patient failed to complete puberty. In all the other seven sexual maturation is normal and one has fathered two children. We conclude that pituitary implantation with interstitial irradiation is a satisfactory form of treatment for Cushings disease in juveniles.

Serum T4, T3, and TSH levels in primary hypothyroidism during replacement therapy with thyroxine

Forty-five patients with primary hypothyroidism were studied during the first 4 to 36 months of replacement therapy with thyroxine. All became clinically euthyroid (23 patients while taking 0.1 mg/d, 14 patients while taking 0.15 mg/d, 7 patients while taking 0.2 mg/d, and 1 patient while taking 0.25 mg/d) over a period of three to six months. The patients were then divided for data analysis into two groups. Group I had normal serum T3 levels, normal (or elevated) serum T4 levels, and normal serum TSH levels. Group II had normal serum T3 levels, normal (or elevated) serum T4 levels, but high serum TSH levels. Group II was subdivided further into a group of 13 patients (group IIa) whose dose of thyroxine was deliberately increased until the serum TSH level was normalized; five of these patients became clinically and biochemically hyperthyroid. Group IIb consisted of eight patients with normal serum T3 and T4 levels and high serum TSH levels who were followed up without attempting to normalize their serum TSH levels. None became thyrotoxic, and their serum TSH levels showed little change. These findings suggest that serum TSH levels alone are not adequate to assess the required dose of thyroxine replacement therapy.

Deoxycorticosterone and aldosterone excretion in Cushing's syndrome

We have used specific radioimmunoassays to measure urinary free deoxycorticosterone (DOC) and total aldosterone excretion in 15 patients with Cushings syndrome. Free DOC excretion was increased in 6 of 8 patients with pituitary-dependent adrenal hyperplasia, in 2 of 3 patients with adrenal adenoma, and in all 4 cases with adrenal carcinoma. The most marked increase was noted in the adrenal carcinoma cases. Aldosterone excretion was high, normal, or low in each of the three types of Cushings syndrome. The free DOC response to metyrapone in Cushings syndrome due to adrenal adenoma was markedly different from that in patients with adrenal hyperplasia (pituitary-dependent) and may serve as a test to ascertain the etiology of the disorder. Correlations of free DOC and aldosterone excretion with free cortisol excretion, and their responses to the administration of metyrapone and dexamethasone were compatible with ACTH dependency in adrenal hyperplasia, autonomous production of steroids in adrenal adenomas and a chaotic steroidogenesis in adrenal carcinoma.