We studied various tests of thyroid function in sick patients with nonthyroidal illness (NTI) in order to determine the utility of each test for differentiating these patience from a group with hypothyroidism. We evaluated each test in 22 healthy volunteers who served as controls, 20 patients with hypothyroidism, 14 patients admitted to medical intensive care unit whose serum T4 was less than 5 micrograms/dl, 13 patients with chronic liver disease, 32 patients on chronic hemodialysis for renal failure, 13 ambulatory oncology patients receiving chemotherapy, 16 pregnant women, 7 women on estrogens, and 20 hyperthyroid patients. On all samples, we measured serum T4, the free T4 index by several methods, free T4 by equilibrium dialysis, free T4 calculated from thyronine-binding globulin (TBG) RIA, free T4 by three commercial kits (Gammacoat, Immophase, and Liquisol), T3, rT3, and TSH (by 3 different RIAs). Although all of the methods used for measuring free T4 (including free T4 index, free T4 by dialysis, free T4 assessed by TBG, and free T4 assessed by the 3 commercial kits) were excellent for the diagnosis of hypothyroidism, hyperthyroidism, and euthyroidism in the presence of high TBG, none of these methods showed that free T4 was consistently normal in patients with NTI; with each method, a number of NTI patients had subnormal values. In the NTI groups, free T4 measured by dialysis and the free T4 index generally correlated significantly with the commercial free T4 methods. Serum rT3 was elevated or normal in NTI patients and low in hypothyroid subjects. Serum TSH provided the most reliable differentiation between patients with primary hypothyroidism and those with NTI and low serum T4 levels.

High levels of thyrotropin releasing hormone (TRH) and TRH-homologous peptide, with the general structure pGlu=X-Pro-NH2 where X is either Histidine (His) or a neutral amino acid residue, have been identified in rat and human prostate (Pekary et al, 1980, 1981a, 1982c). Because of the secretory nature of prostatic tissue, it was considered likely that these peptides would be measurable in human semen. The mean (+/- SD) TRH immunoreactivity (TRH IR) in semen from 26 normal donors, aged 26 and 41 years, was found to be 12.2 +/- 5.2 ng/ml. TRH and TRH-homologous peptide, were undetectable in unconcentrated human serum. TRH IR levels in semen from azoospermic donors were in the normal range. The level of TRH IR in semen from vasectomized donors was significantly less (P less 0.01) than in semen from normal subjects. Evidence for at least two TRH-binding substances, which coextract and bind to added synthetic TRH, was obtained by exclusion and cation exchange chromatography. Purification of extracts of human semen by TRH affinity chromatography or gradient, reversed phase high pressure liquid chromatography (HPLC) revealed two major TRH immunoreactive peptides, one corresponding to the TRH-homologous peptide previously reported in rat and human prostate and one cochromatographing with synthetic TRH.

The hyperthyroid state in vivo is associated with an increase in osteoblast number and activity, suggesting that thyroid hormone may stimulate osteoblast replication and function. We therefore examined the effects of T3 (16-1170 pM) on replication rate as assessed by cell counts in UMR-106 osteoblastic osteosarcoma cells cultured for 5-10 days in medium supplemented with 10% hormone-stripped fetal calf serum (FCS). Despite the virtual absence of thyroid hormone in the control medium (total T3 concentration, 0.02 ng/ml), the addition of T3 in concentrations to 1000 pM did not increase the cell replication rate. At higher T3 concentrations, a slight decrease in growth rate was observed. No significant 5'-monodeiodinase activity was detected in UMR-106 cell homogenates. However, nuclear binding of T3 was demonstrated in intact cells. A high-affinity nuclear binding component was identified with a Ka of 2.6 x 10(10) M-1 and a maximum binding capacity of 7.7 pg T3 per mg DNA, equivalent to 51 binding sites per cell nucleus. A lower affinity nuclear T3 binding component with a Ka of 1.8 x 10(9) M-1 was also identified. Thus, despite the presence of nuclear T3 receptors, UMR-106 cells do not exhibit a mitogenic response to T3.

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Abstract. Pituitary thyrotrope tumours are a rare cause of hyperthyroidism. Prior in vitro studies of these tumours have revealed various patterns of differentiation and secretory activity. We have characterized the histological, biochemical, molecular and physiological features of a thyrotrope adenoma in order to define its origin and autonomy. Histochemical and electron micrograph findings confirmed the diagnosis of a thyrotrope cell adenoma. Immunostaining was positive for TSH and GH in the cytoplasm of the adenoma cells. Tissue extracts contained TSH-IR which co-eluted with authentic hTSH when analysed by gel filtration. Tumour fragments studied in a tissue culture system secreted TSH, α-subunit and GH. TRH (30 nmol/l) stimulated TSH and GH secretion. T3 (1.5 nmol/l) inhibited GH release and had no effect on TSH secretion. GnRH (50 nmol/l), dexamethasone (10−4 mol/l), SRIH (1 μmol/l) and TRH-glycine, a tetrapeptide precursor of TRH, stimulated TSH release. Dexamethasone inhibited GH and α-subunit secretion. Stable transcripts for α- and β-subunits of TSH and GH messenger RNAs were detected by molecular hybridization in cytosolic fractions. Immunohistochemistry, in vitro secretory function, and mRNA analysis suggest multidirectional differentiation of the tumour cells. TRH-glycine may have a direct stimulatory effect upon pituitary thyrotropes.

In the present study we have examined the in vivo effects of thyroid hormone and TRH on secretory tissue concentrations of TRH and TRH-Gly (pGlu-His-Pro-Gly), a TRH precursor. Within secretory granules, TRH-Gly is converted to TRH through alpha-amidation of the C-terminal proline residue, using Gly as the NH2 donor. Using specific RIA, we measured the TRH-Gly immunoreactivity (TRH-Gly-IR) and TRH-IR concentrations in tissues from the reproductive and gastrointestinal systems, adrenals, and other internal organs in euthyroid, hypothyroid, and T4-treated 250-g Sprague-Dawley male rats. TRH-Gly-IR concentrations were more than 2-fold higher than TRH-IR concentrations within the adrenal, pancreas, bowel, and stomach at the time of death. Untreated hypothyroidism and exogenous TRH significantly increased adrenal TRH-Gly-IR levels. Pancreatic TRH-Gly levels increased about 2-fold in hypothyroid rats. Incubation at 60 C significantly increased TRH-Gly-IR levels in the pancreas, adrenal, bowel, stomach, and epididymis by 14-, 3-, 6-, 6-, and 6-fold, respectively. Also after 60 C incubation increases in the TRH-Gly-IR/TRH-IR ratio of 2.7-, 4-, and 1.7-fold were observed in the pancreas, epididymis, and bowel, respectively. Pooled tissue extracts were fractionated by cation exchange and reverse phase HPLC for characterization of TRH-Gly-IR. Both chromatographic methods revealed a major peak of TRH-Gly-IR coeluting with synthetic TRH-Gly. Incubation at 60 C caused 13.5-, 4.1-, 1.5-, and 5-fold increments in the TRH-Gly-IR for adrenal, pancreas, prostate, and thyroid, respectively, compared to the immediately extracted control aliquots. Cation exchange and reverse phase HPLC also revealed production of higher mol wt TRH precursor peptides after incubation at 60 C for 4 or 20 h. Only the TRH-Gly-IR peak coeluting with pGlu-His-Pro-Gly was converted into TRH by rat brain alpha-amidating enzyme. The data suggest that biosynthesis of TRH occurs in rat extrahypothalamic tissues and may be modulated by thyroid status, iv TRH, and selective thermal inactivation of enzymes that convert prepro-TRH to TRH.

The plasma clearance rate (PCR) and plasma half-disappearance time (t1/2) of TRH was compared to the PCR and t1/2 of pyroglutamyl-N3im-methyl-histidyl prolineamide (methyl-TRH), a more potent analog of TRH in normal subjects. The PCR for TRH was 1500 +/- 329 (SD) ml/min, which was significantly greater than the PCR of methyl-TRH (783 +/- 96 ml/min). The t1/2 of TRH was 6.2 min compared to a t1/2 of 11.5 min for methyl-TRH. The slower clearance of methyl-TRH is probably due to the increased resistance to degradation by serum enzymes of methyl-TRH compared to TRH.

Thyrotropin releasing hormone (TRH) immunoreactive peptides occur in high concentration within rat ventral prostate and human semen. To extend these observations to human reproductive organs, tissue fragments from human prostates undergoing benign hypertrophy were obtained by transurethral resection or open surgery. Human prostate, seminal vesicles, testes, and epididymis were also obtained from cadavers within 24 hours postmortem. After tissue extraction, the total TRH immunoreactivity (TRH IR) was measured by TRH radioimmunoassay. The total TRH IR in autopsy seminal vesicles was significantly greater (P < 0.01) than in all other autopsy reproductive tissues. The mean autopsy TRH IR of prostate was not significantly different from that measured in prostatic tissue obtained at surgery. High pressure liquid chromatography of extracts of autopsy seminal vesicles, prostate, and testis revealed multiple peaks of TRH IR. The two major peaks corresponded to the two TRH‐homologous peptides of human semen and one of the minor peaks cochromatographed with synthetic TRH. The distribution of TRH IR in human reproductive tissues appears to be very different from that in the rat, where ventral prostatic TRH IR levels exceed that of any other reproductive tissue by one to two orders of magnitude.