No abstract

The initial presentation of macroprolactinoma with visual field impairment, especially in males, is well recognized. Successful treatment with dopamine agonist therapy is characterized by a reduction in hyperprolactinaemia and often rapid and progressive resolution of the visual impairment. A small proportion of patients may subsequently develop a secondary deterioration in both their visual fields and visual acuities despite normalization of prolactin levels and tumour shrinkage. When pituitary apoplexy can be excluded this may result from traction on the optic chiasm which is pulled down into the now partially empty sella. We report a series of seven patients in whom chiasmal traction is believed to be the cause of their secondary deterioration in visual acuity occurring after dopamine agonist therapy for macroprolactinoma. The clinical history of two patients both of whom had rapid resolution of field defect with bromocriptine therapy but subsequently developed a recurrence of their bitemporal hemianopia is detailed. In both patients MRI scanning showed not only tumour involution but also marked optic chiasm herniation into the pituitary fossa. Surgical treatment was considered too risky; but on reduction of bromocriptine dosage the field defect improved in both cases; there was a modest elevation of prolactin and a degree of tumour re-expansion. The latter is believed to have released tethering of the optic chiasm and/or its vascular supply and thus obviated the need for surgery. Regular monitoring of visual fields in patients with macroprolactinoma receiving medical treatment is therefore important. Early recognition of secondary field loss due to chiasmal herniation enables correction of the visual field loss by manipulation of the medical therapy.

No abstract

No abstract

A particulate membrane fraction from human placental membrane was shown to be rich in binding sites not only for insulin but also for somatomedin A. The binding of the 125I-labelled peptide was time and temperature dependent. Degrading activity present in the membrane fraction was negligible at +4\s=deg\C. The Scatchard plot for insulin binding revealed two types of binding sites with an apparent high affinity constant of 3.8\m=x\ 108 m\ m=-\ 1 and with 5.4 \ m=x\10\m=-\9 moles of binding sites per mg of membrane protein. The Scatchard analysis of somatomedin A revealed two classes of binding sites with an apparent high affinity constant of 2.7 \m=x\107 m\ m=-\ 1 and with 1.9\m=x\10\m=-\8moles of binding sites per mg of membrane protein. In high concentrations insulin interfered with the specific binding sites for somatomedin A and vice versa. In comparison with insulin the somatomedin A preparation was one million times more potent in displacing labelled somatomedin A than in displacing labelled insulin from their respective binding sites. A radioreceptor assay utilizing particulate placental membrane and labelled somatomedin A purified on the membrane enabled the determination of somatomedin in unextracted serum. The mean values of somatomedin A in sera from patients with pituitary dwarfism and acromegaly were 0.57 and 3.2 U/ml, respectively by radioreceptor assay and 0.41 and 1.61 U/ml, respectively by bioassay. Various causes of this discrepancy between the methods are discussed.