triiodothyronine--reverse and Hyperparathyroidism

Although patients with primary hyperparathyroidism (1 degree HPT) were euthyroid, we measured serum thyroid hormone levels in 16 patients with 1 degree HPT together with 17 patients with hypercalcemia due to malignant diseases (HCM). In patients with 1 degree HPT, serum levels of T3, T4 and T3U were within normal range, but serum rT3 (reverse T3) levels (205 +/- 37 pg/ml, mean +/- SD) were significantly decreased as compared with those in normal controls (276 +/- 44 pg/ml, P less than 0.01). A significant inverse correlation was observed between the serum levels of rT3 and parathyroid hormone (PTH) (r = 0.54, P less than 0.05). After parathyroidectomy, serum rT3 levels were significantly elevated (240 +/- 56 pg/ml) compared to preoperative levels (P less than 0.01). Low levels of serum rT3 seemed to be attributed to the high levels of serum PTH. On the other hand, serum levels of T3 and T4 were low and serum rT3 levels were high in patients with HCM. Low serum rT3 allows for the differentiation of patients with 1 degree HPT from those with HCM.

Topics: Adolescent; Adult; Aged; Female; Humans; Hypercalcemia; Hyperparathyroidism; Male; Middle Aged; Neoplasms; Parathyroid Hormone; Thyroid Hormones; Triiodothyronine, Reverse

Serum total reverse triiodothyronine (rT3) levels are normal in patients with renal diseases with and without renal insufficiency but elevated in nonrenal nonthyroidal illnesses. To evaluate the role of secondary hyperparathyroidism of renal diseases in this difference, serum thyroid hormone levels were studied in 27 patients with primary hyperparathyroidism (PHP) and normal renal function. In PHP, total T3 levels were reduced (118 +/- 6 ng/dL, normal: 147 +/- 3 ng/dL) and correlated with PTH levels. Serum rT3 levels were also decreased (27 +/- 3 ng/dL, normal: 34 +/- 2 ng/dL). Values for serum total thyroxine (T4), T3 uptake ratio, free T4 index, and thyrotrophin were not altered. Serum rT3 levels were increased (63 +/- 13 ng/dL) in patients with hypercalcemia due to malignant neoplasms who had low T3 levels, undetectable PTH and normal renal function. Thus, PTH excess may be the factor responsible for the failure of rT3 levels to increase in PHP and secondary hyperparathyroidism.

Topics: Adult; Aged; Female; Glomerular Filtration Rate; Humans; Hyperparathyroidism; Male; Middle Aged; Parathyroid Hormone; Thyroid Hormones; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

The thyroid hormone secretory response to TSH was studied in twenty-eight patients undergoing thyroid and parathyroid surgery. Eighteen patients received bovine or human exogenous TSH by injection into a thyroid artery, and 10 received TRH to stimulate endogenous TSH secretion. Thyroid secretion rates of T4, T3, and rT3 were determined directly from measurement of blood flow and the hormone gradient across the gland. A significant secretory response was seen for all three hormones following TSH increase. T3 secretion accelerated more rapidly than that of T4 and rT3, thus reducing the T4/T3 and rT3/T3 ratios. The T4/rT3 ratio fell during the first 30 min but then increased. The responses correlated with the area under the curve of the TSH serum concentration, and were similar after administration of bovine and human exogenous TSH, and TRH. Conclusions regarding preferential secretion ought to be made by comparing ratios of thyroid hormone secretion with those of the hormone content of the gland, but our results indicate that TSH induces preferential secretion of triiodothyronines in man.

Topics: Adult; Aged; Female; Humans; Hyperparathyroidism; Male; Middle Aged; Secretory Rate; Thyroid Gland; Thyroid Hormones; Thyroidectomy; Thyrotropin; Thyrotropin-Releasing Hormone; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

The secretion rates of T4, T3, and rT3 were studied in experiments of short duration by a new method based on determinations of the hormone difference across the thyroid combined with simultaneous electromagnetic thyroid blood flowmetry during surgery in 70 euthyroid patients. The secretion rate of T3 was similar in normal thyroid tissue and nodular goitre, but those of T4 and rT3 were lower in nodular goitre and solitary adenoma (P less than 0.05). In 61 patients with normal thyroid tissue or nodular goitre the secretion rates during surgery (mean +/- SEM) were for T4 222 +/- 28 nmol/day, for T3 27.4 +/- 3.1 nmol/day, and for rT3 3.5 +/- 0.5 nmol/day. In relation to the individual T4 secretion rate, the secretion rate of T3 was 12.5 +/- 3.0% and that of rT3 1.2 +/- 0.9%. In these short-term experiments we found a secretion rate for T4 during operation about 50% greater than in earlier long-term kinetic studies, but which tallied with a recent report using a 4-compartment model. For T3 and rT3 it was 2-3 times greater than earlier estimates. The secretion was estimated to be 50% of the total production rate for T3 and 6% for rT3. If proportional adjustment were performed to yield a T4 secretion of about 130 nmol/day. T3 and rT3 secretion rates would still be greater than earlier reported.

Topics: Adenoma; Adult; Aged; Carcinoma; Electromagnetic Phenomena; Female; Goiter; Goiter, Nodular; Humans; Hyperparathyroidism; Intraoperative Period; Male; Middle Aged; Rheology; Surgical Procedures, Operative; Thyroid Gland; Thyroid Neoplasms; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse