propylthiouracil and Acromegaly

Topics: Acromegaly; Adrenocorticotropic Hormone; Aminoglutethimide; Bromocriptine; Calcitonin; Cushing Syndrome; Diazoxide; Diphosphonates; Estrogens; Fluid Therapy; Hemangiopericytoma; Humans; Hypercalcemia; Hyperthyroidism; Hypoglycemia; Inappropriate ADH Syndrome; Ketoconazole; Mifepristone; Mineralocorticoids; Mitotane; Octreotide; Osteomalacia; Pamidronate; Paraneoplastic Endocrine Syndromes; Phosphorus; Plicamycin; Propylthiouracil; Saline Solution, Hypertonic; Somatostatin; Thyroid Neoplasms

The activity of T4 5'-monodeiodinase (5'D) in the pituitary was measured in 12 patients with pituitary adenoma (3 patients with acromegaly, 2 with prolactinoma, 1 with Cushing's disease, 1 with TSH-producing tumor, and 5 with nonfunctioning tumor) and, as a control, in a patient who died of parotid cancer. The pituitaries, obtained at operation or autopsy, were homogenized in 0.1 mol/L potassium phosphate buffer, pH 7.0, and centrifuged at 800 x g. Supernatants were incubated with [125I]T4 and 20 mmol/L dithiothreitol (DTT) at 37C for 90 min. T4 5'-D was measured by the release of 125I- with the ion exchange method. The activity of T4 5'-D in the pituitaries from patients with prolactinoma and parotid cancer was dependent on protein concentration, incubation time, incubation temperature, and T4 concentration, and was labile to prior heating at 70 C for 30 min. T4 5'-D was not inhibited by 1 mmol/L propylthiouracil, but was inhibited 95% by 0.1 mmol/L iopanoic acid. The apparent Km and maximum velocity for T4 5'-D in homogenates of prolactinoma at 20 mmol/L DTT were 11 nmol/L and 1.54 pmol/mg protein.h, respectively. This reaction followed sequential-type reaction kinetics when the DTT concentration was varied. All other homogenates of pituitary tumors, except two nonfunctioning tumors, also demonstrated T4 5'-D activity. These results indicate that 1) the human pituitary express a low Km and PTU-insensitive T4 5'-D activity which is very similar to the type II enzyme activity in the rat pituitary; and 2) various types of pituitary tumor cells contain T4 5'-D activity.

Topics: Acromegaly; Adult; Dithiothreitol; Female; Humans; Iodide Peroxidase; Kinetics; Male; Middle Aged; Pituitary Gland, Anterior; Pituitary Neoplasms; Prolactin; Propylthiouracil

A 44-year-old man subjected to Hardy's operation for a treatment of acromegaly developed hyperthyroidism right after surgery. He had a normal thyroid function with a slightly suppressed TSH response to TRH before operation. Sudden onset of hyperthyroidism after surgery and suppressed TSH were compatible with Graves' disease. Hyperthyroidism was effectively treated with propylthiouracil (PTU) with slightly increased basal TSH level and normal response of TSH to TRH. Plasma GH level also increased after he attained euthyroidism, but inappropriate GH response to TRH persisted. It is suggested that increased endogenous TRH stimulated both TSH and GH release, but inappropriate GH response to TRH occurred irrespective of endogenous hypothalamic TRH. Bromocriptine, 5.0 mg/day, suppressed plasma GH level to a normal range with a concomitant suppression of PRL and TSH, both basal levels and responses to TRH.

Topics: Acromegaly; Adult; Bromocriptine; Graves Disease; Growth Hormone; Humans; Male; Propylthiouracil; Thyrotropin; Thyrotropin-Releasing Hormone

Topics: Acromegaly; Female; Growth Hormone; Humans; Hyperthyroidism; Menopause; Methimazole; Middle Aged; Prednisolone; Prolactin; Propylthiouracil; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse