Complications of surgery in hypothyroid patients.

Hypothyroidism has generally been considered a contraindication to surgery. To determine the actual risks of perioperative complications in hypothyroid patients, the clinical courses of 40 hypothyroid surgical patients (serum thyroxine concentration 1.9 +/- 1.

L-Thyroxine therapy in subclinical hypothyroidism. A double-blind, placebo-controlled trial.

The indications for treating patients with subclinical hypothyroidism (normal serum thyroxine and free thyroxine levels, but elevated serum thyrotrophin levels) are poorly defined. In this study, 33 patients with subclinical hypothyroidism were randomly assigned in a double-blind manner to receive placebo or L-thyroxine therapy and were followed for 1 year with thyroid function tests, serum lipid measurements, basal metabolic rate and systolic time interval determinations, and a questionnaire on hypothyroid symptoms. The placebo group showed no changes in thyroid function or peripheral indices of thyroid hormone action.

Gonadotropin and prolactin pulsations in hyperprolactinemic women before and during bromocriptine therapy.

Pulsatile gonadotropin secretion and its relationship to PRL and estradiol (E2) secretion were investigated in 20 hyperprolactinemic amenorrheic women by obtaining serial blood samples for 6- to 24-h periods. Thirteen patients were restudied in the early follicular phase of the menstrual cycle (days 3-5) after ovulatory periods were established during bromocriptine therapy. In the hyperprolactinemic women, the number of LH peaks ranged from 0-12/24 h, and LH peak amplitude ranged from 0-1.

Follicle-stimulating hormone-secreting pituitary tumor with concomitant elevation of serum alpha-subunit levels.

Hypersecretion of FSH and alpha-subunit was documented in a man with a pituitary adenoma that was previously diagnosed on clinical grounds as nonfunctioning who had been treated by transsphenoidal surgery and postoperative irradiation. Postoperatively, the patient had high serum FSH levels and normal serum, LH levels. Ten years after the surgery, immunostaining of the tumor revealed the presence of beta FSH, beta LH, and beta TSH in the cytoplasm of scattered adenoma cells, although not always in the same cells.

Discordant changes in pituitary concentrations of LH and TSH subunits following hormonal manipulation.

We have recently shown that mouse pituitary concentrations of free TSH-beta and alpha-subunits respond divergently to thyroid hormone manipulations in vivo. This study contrasts the changes in free LH-beta and alpha-subunits after castration and polyestradiol phosphate (E2) administration with those in free TSH-beta and alpha-subunits after thyroidectomy and thyroxine (T4) administration. Target hormone depletion (castration or thyroidectomy) resulted in an increase in plasma concentrations of the respective tropic hormones and their subunits; target hormone administration (E2 or T4) resulted in a decrease in plasma concentrations.

Methimazole pharmacology in man: studies using a newly developed radioimmunoassay for methimazole.

A RIA for the antithyroid drug methimazole [1-methyl-2-mercaptoimidazole (MMI)] has been developed. A MMI derivative, 5-COOH-MMI, was conjugated to porcine thyroglobulin, and antibodies to the conjugate were raised in rabbits. [35S]MMI was used as the tracer.

Methimazole pharmacology in the rat: studies using a newly developed radioimmunoassay for methimazole.

Methimazole [1-methyl-2-mercaptoimidazole (MMI)] was given to normal male rats in their drinking water in concentrations ranging from 0.0001-0.05% for either 1 week or 1 month.

Calcium sensitivity is modified by contraction.

This paper summarizes three lines of experimental evidence showing that crossbridge interaction affects calcium sensitivity and probably also affects calcium binding. Evidence is presented that this is a true hysteresis, not just a slow approach to equilibrium. In barnacle single muscle fibers injected with aequorin to monitor intracellular Ca, a long duration stimulus under voltage clamp conditions can produce a long duration calcium transient and force record which both approach steady levels.

Muscle calcium transient. Effect of post-stimulus length changes in single fibers.

We examined the effects of post-stimulus length changes on voltage-clamped, aequorin-injected single muscle fibers from the barnacle Balanus nubilus. Extra light (extra calcium) is seen when the fiber is allowed to shorten (a small percentage) during the declining phase of the calcium transient. The opposite is observed when the fiber is stretched.

Regulation by thyroxine of the mRNA encoding the alpha subunit of mouse thyrotropin.

Thyrotropin (TSH), a glycoprotein hormone of the pituitary consisting of two subunits (alpha and beta), regulates thyroxine (T4) production by the thyroid gland. T4, in turn, regulates TSH biosynthesis and release. We have studied the regulation of the messenger RNA encoding the alpha subunit of TSH by T4 in pituitaries and in a transplantable thyrotropic tumor in mice.

Mouse pituitary tumor line secreting only the alpha-subunit of the glycoprotein hormones: development from a thyrotropic tumor.

This report describes the conversion of a murine pituitary thyrotropic tumor (MGH 101) to a pure alpha-subunit-secreting tumor (MGH 101A) during a 6-yr period of serial transplantation. MGH 101 was a thyrotropic tumor originating from a hypothyroid mouse pituitary, growing only in hypothyroid hosts, and secreting large quantities of intact TSH and free alpha-subunit. Between the fourth and ninth transplantation generations, tumor TSH secretion declined progressively by at least 500-fold, to undetectable levels.

Pure alpha subunit-secreting pituitary tumors.

The authors describe six patients with pituitary macroadenomas hypersecreting only the alpha subunit of the glycoprotein hormones. These patients had been previously diagnosed as having "non-functioning chromophobe adenomas." All of the patients had visual field abnormalities and partial hypopituitarism.

Direct adrenergic stimulation of the release of thyrotropin and its subunits from the thyrotrope in vitro.

Adrenergic effects on TSH and subunit secretion were investigated in bovine anterior pituitary monolayer cultures. Epinephrine (E) (10(-6) M) caused a significant increase in TSH, alpha-subunit, and TSH beta release into the medium (P less than 0.001, P less than 0.

Propylthiouracil (PTU) pharmacology in the rat. II. Effects of PTU on thyroid function.

Using a sensitive and specific RIA for propylthiouracil (PTU), we examined the effects of short term (1 week) and long term (1 month) PTU treatment on thyroid function in the rat, and correlated changes in thyroid function with serum and thyroid PTU levels. After 1 week, dose-dependent decreases in thyroid PBI, serum T4, and serum T3 were observed, with concomitant elevations in the serum rT3 to T4 ratio and serum TSH. Fifty percent suppression of thyroid PBI occurred at a PTU concentration in the drinking water of 0.

Propylthiouracil (PTU) pharmacology in the rat. I. Serum and thyroid PTU measurements by radioimmunoassay.

We have developed a highly sensitive and specific RIA for propylthiouracil (PTU) which uses 125I-labeled PTU as the radioactive ligand. At a final antibody dilution of 1:10,000, the detection limit for PTU was 100 pg; cross-reactivity with circulating, urinary, and intrathyroid PTU metabolites was negligible. Using this assay, serum and thyroid PTU levels were determined after short term (1 week) and long term (1 month) PTU treatment at doses of 0.

Use of adjunctive potassium iodide after radioactive iodine (131I) treatment of Graves' hyperthyroidism.

One hundred and nineteen patients with Graves' hyperthyroidism who were treated with 131I alone or 131I followed by potassium iodide (131I + KI) were studied retrospectively. Patients in both groups who required only a single dose of 131I for successful treatment of hyperthyroidism had similar age, gland size, 24-h radioactive iodine uptake, pretreatment serum T4 concentrations, and radioactive iodine treatment dose. Seven weeks after 131I, mean serum T4 concentrations were 12.

Changes in tissue concentrations of thyrotropin, free thyrotropin beta, and alpha-subunits after thyroxine administration: comparison of mouse hypothyroid pituitary and thyrotropic tumors.

We have previously demonstrated divergent changes in pituitary free TSH beta and alpha-subunit concentrations in hypothyroid mice during prolongation of experimental hypothyroidism and after T4 administration. This report compares the simultaneous responses of pituitary and thyrotropic tumor TSH, TSH beta, and alpha-subunit to 12 days of T4 administration in four groups of hypothyroid LAF1 mice bearing thyrotropic tumors. Half of each group received daily injections of T4 (10 micrograms/100 g BW, ip) for 12 days; the other half of each group received saline.

Rapid pituitary and peripheral tissue responses to intravenous L-triiodothyronine in hypothyroidism.

Acute cardiovascular, renal, pulmonary, metabolic, and pituitary responses to therapy of hypothyroidism with 25 micrograms iv T3 (group I G-I, n = 11) or 50 micrograms iv T3 (group II, G-II, n = 10)/day for 1 week have been studied. Serum T3 levels were acutely normalized in both groups with the mean basal serum T3 levels (X +/- SE) after 7 days, 98 +/- 10 micrograms/dl and 229 +/- 19 ng/dl, respectively. Myocardial performance, noninvasively assessed by the pulse wave arrival time (QKd) and the phonocardiographic systolic time interval ratio was significantly altered after 1 day of therapy (QKd for G-I = -10 +/- 4 msec, P less than 0.

The effect of somatostatin on the release of thyrotropin and its subunits from bovine anterior pituitary cells in vitro.

The effects of somatostatin (SRIF) on the production and release of TSH and its subunits have been investigated in bovine anterior pituitary monolayer cultures. SRIF caused a dose-dependent inhibition of TSH and subunit release by TRH, with a half-maximal effective dose of 3 X 10(-8) M. This effect was time dependent and was greater for TSH than for its subunits.

Sequestered substernal goiter.

A young woman with a normally located and only subtly nodular thyroid gland in the neck was found to have a clinically distinct and radioisotopically "cold" anterior mediastinal mass, which proved to be a benign colloid adenoma. While this constellation of findings usually suggests the presence of a nonthyroidal neoplasm, eg, lymphoma, thymoma, or teratoma, our case illustrates that sequestered benign nodular goiter should also be considered in the differential diagnosis. Clinical clues, such as a nodular thyroid gland, movement of the mass with deglutition, and a family history of nodular goiter, should suggest this possibility.

Elevated thyroxine levels due to increased thyroxine-binding globulin in acute hepatitis.

Two patients are presented who had unexpected increases in serum thyroxine concentration due to acquired thyroxine-binding globulin excess associated with asymptomatic hepatitis. Serum hormone concentrations were also analyzed retrospectively in 10 outpatients with viral hepatitis. Acute hepatitis is associated with an increase in serum thyroxine and thyroxine-binding globulin concentrations and a corresponding decrease in the triiodothyronine resin uptake.

alpha-Subunit and gonadotropin responses to luteinizing hormone-releasing hormone in hyperprolactinemic women before and after bromocriptine.

alpha-Subunit and gonadotropin responses to a LHRH infusion (0.2 micrograms/min) for 4 h were studied in eight hyperprolactinemic amenorrheic women, ages 23-40, and in five normal women in the early follicular phase of the menstrual cycle. Basal alpha-subunit and LH concentrations were comparable to normal women; however, basal FSH concentrations were significantly (P less than 0.

Hysteresis in the force-calcium relation in muscle.

Calcium ions activate muscle contraction. The mechanism depends on the calcium sensitivity of the proteins that regulate contraction. Evidence is presented for the reverse phenomenon, where contraction modulates calcium sensitivity.

Dopaminergic modulation of TSH and its subunits: in vivo and in vitro studies.

We have studied the effects of dopamine on the secretion of TSH and its subunits in vivo and in vitro. Four normal controls, seven patients with primary hypothyroidism, two patients with peripheral resistance to thyroid hormone (PRTH), and two patients with alpha-secreting pituitary tumours underwent a 3-h dopamine infusion (4 micrograms/kg/min). Serial blood samples were drawn for TSH, PRL, alpha, and TSH-beta subunit.