SUMMARY The pars intermedia of the rat pituitary contains a peptide resembling the 18–39 portion of adrenocorticotrophic hormone (ACTH), which has been termed 'corticotrophin-like intermediate lobe peptide' (CLIP). It can be detected by its cross-reaction with an antiserum directed against the CO2H-terminal portion of the ACTH molecule; it has an amino acid composition identical to the 18–39 portion of human ACTH, except for one less glycine and an extra valine residue, and it is rapidly released from neurointermediate lobes maintained in organ culture. The pars intermedia also contains a peptide with an amino acid composition and biological potency identical to that of melanocyte-stimulating hormone (α-MSH) isolated from other mammals, and which accounts for the bulk of melanocyte-stimulating activity in the pituitary. Rat ACTH resembles human ACTH in amino acid composition, except for an extra valine and one less glycine residue. On the basis of these data it is proposed that ACTH is the precursor of α-MSH and CLIP, which are both present in the cells of the pars intermedia.

The thyroid status of 82 institutionalized adults with Down's syndrome has been assessed. Compared to age and sex matched control subjects, these patients had significantly lower mean total serum thyroxine (T4) and triiodothyronine (T3) concentrations (T4; 69.1+/-22.2 nmol/1; (mean+/-SD) vs. 100.1+/-19.1, P less than 0.001; T13; 1.61+/-0.47 nmol/1 vs. 1.76+/-0.34, P less than 0.025), lower free thyroxine index (FTI), (FTI; 66.1+/-22.4 vs. 95.1+/-20.2, P less than 0.001), and higher basal serum thyrotrophin (TSH) concentrations (TSH; 7.6+/-10.7 mU/1 vs. 3.8+/-1.5, P less than 0.001). These changes were not related to age or sex. Abnormalities in one or more test of thyroid function were demonstrated in at least 38 (46%) of the 82 patients. Two main patterns of abnormality were defined: 1) subnormal T4, FTI and elevated basal TSH levels (primary hypothyroidism) in 13 (16%). All seven of the 13 patients in whom TRH tests were performed showed the expected exaggerated TSH response, and seven out of the 13 patients (54%) had positive thyroid antibodies, 2) Subnormal T4, subnormal or low normal FTI, and basal TSH levels within the normal range in 18 (22%). The mean basal TSH concentration was, however, significantly higher than in patients with normal T4 and FTI levels, suggesting a minor degree of thyroid failure. Only two of the 18 patients (11%) had positive thyroid antibodies. Of the 17 patients in the group tested, 13 showed a normal TSH response to TRH, three an exagerrated response (all females), and one had an impaired response. Other patterns of abnormal thyroid function were observed occasionally: one female patient had biochemical T3 toxicosis; another had the biochemical pattern of subclinical hypothyroidism, four patients with normal basal T4, FTI and TSH levels showed an exaggerated TSH response to TRH and one patient had an impaired response. These data indicate that htyroid dysfunction, in particular hypothyroidism, is common in adults with Down's syndrome, though specific tests are usually required to make the diagnosis. The general reduction in thyroid function in Down's syndrome may be due to impaired development of the thyroid gland. However, frank chemical hypothyroidism may occur only when thyroiditis is superimposed on preexisting diminished thyroid reserve.

No abstract

No abstract

Specific binding of 125I-labelled ovine prolactin iodinated by a lactoperoxidase method was demonstrated in crude membrane preparations of kidneys and adrenals of male Sprague-Dawley rats and livers from female rats. Membrane preparations derived from the 100,000 g fractions of tissue homogenates contained most of the specific prolactin binding. Kinetic and affinity characteristics of prolactin binding to kidney membranes were examined in detail. Maximal specific binding occurred after incubation for 30 h at room temperature. Scatchard analysis indicated that prolactin binding to kidney membranes was of high affinity (dissociation constant = 1.4 x 10(-10) mol/l) and similar to that for liver membranes, although kidney membranes from male rats bound approximately sixfold less prolactin/mg membrane protein than did liver membranes from female rats. Specific prolactin binding was demonstrated in both renal medulla and cortex. Autoradiography showed maximal prolactin binding activity in the epithelial cells of the proximal tubule and faint activity in the tubular cells throughout the nephron. Specificity of uptake by proximal tubular cells was indicated by the gross reduction in prolactin activity when excess ovine prolactin was administered simultaneously. The demonstration of specific binding sites for prolactin localized primarily in the proximal tubules was consistent with renal action of prolactin, predominantly on sodium metabolism.

No abstract

Methods for separating free and antibody-bound hormone in radioimmunoassays for total triiodothyronine (T-3) and thyroxine (T-4) in unextracted human serum are evaluated. For T-3 assay, a simplified second antibody technique has significant advantages over other methods and gives a mean interassay coefficient of variation of 7.2% over a wide range of values. For T-4 assay, polyethylene glycol is the method of choice and has a mean interassay coefficent of variation of 4.7%. By adding the separating agents initially, the assays are readily semi-automated and may be completed within a working day.

SUMMARY Changes in thyroid hormone concentration and distribution and plasma cortisol levels have been followed in 11 patients undergoing elective cholocystectomy. A significant rise in total and free thyroxine (T4) and fall in total and free triiodothyronine (T3) were noted after surgery. Reverse T3 concentrations rose substantially, suggesting that peripheral conversion of T4 to T3 is diminished and that there is preferential formation of reverse T3. Serum thyroid stimulating hormone concentrations did not change. There was no direct correlation between the change in cortisol and the change in thyroid hormone or reverse T3 concentrations.