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Rationale—Microsomal antibodies have been related to postpartum thyroid dysfunction and postpartum depression. Objectives—To detect the value of microsomal antibodies during gestation in a random population, as a risk factor for thyroid dysfunction and depression during the postpartum period. Main findings—The presence of microsomal antibodies was investigated in a random population of 293 women at 32 weeks' gestation. At the same time, postpartum thyroid function was assessed repeatedly in all women every six weeks up to 34 weeks' postpartum. Postpartum thyroid dysfunction, defined as the presence of abnormal TSH, in combination with abnormal fT4 and/or fT3 values, occurred in 21 women (7.2%) during the postpartum period. Depression was assessed using the Research Diagnostic Criteria without knowing the results of biochemical thyroid function tests. At 32 weeks' gestation there were 27 (9.2%) women with elevated microsomal antibody titres. Compared with microsomalantibody negative women at 32 weeks' gestation, these women had an RR of 20 for developing postpartum thyroid dysfunction and an RR of 1.7 for developing postpartum depression. Conclusions—Women with elevated microsomal antibody titres during gestation are particularly at risk for postpartum thyroid dysfunction, but only have a slightly increased risk for postpartum depression.

The present study was designed to assess the quantities of T4 and T3, and the source (i.e. plasma-derived vs. locally produced) of the latter iodothyronine, in various rat tissues. For this purpose, normal intact rats were brought to isotopic equilibrium by means of a continuous iv infusion of [125I]T4 and [131I]T3 for a prolonged period. At the end of the infusion period, the animals were bled and perfused. Either whole small organs or weighed portions of tissues were homogenized in saline. The iodothyronines were extracted with ethanol-ammonia and separated by TLC. The [125I]T3/[131I]T3 ratios for the tissue homogenates and plasma were determined, and the relative contribution of the T3 derived from local T4 to T3 conversion [abbreviated: Lc T3 (T4)] to the total T3 in a given tissue was calculated. The endogenous T4 and T3 levels in the various organs were computed from the known specific activities of the labeled iodothyronines. The concentration of T4 in plasma greatly exceeded that found for tissue. Among the tissues examined, the T4 concentration was highest in the liver and lowest in cerebral cortex and cerebellum. T3 (per gram) was most abundant in the kidney and anterior pituitary gland and least abundant in the testis, epididymis, and erythrocytes. In contrast to the other tissues investigated, the concentration of T3 in several regions of the brain and anterior pituitary gland either equalled or exceeded that of T4. Plasma exhibited by far the lowest T3/T4 ratio. For most of the organs investigated the contribution of Lc T3(T4) appeared to be low. On the other hand, in 15 tissues, including the central nervous system, the local production of T3 accounted for one fifth or more of the total T3 content. Although there were no regional differences between the total T3 levels in the brain, the relative contribution of Lc T3(T4) was 65% in the cerebral cortex and only 22% in the spinal cord. The variation in the source of T3 in the various parts of the central nervous system may be related to regional differences in T4 and T3 metabolism. The fact that the present study demonstrates that the relationship between circulating T3 and intracellular T3 varies from one organ to the next may be important for accurate interpretation of plasma T4 and T3 levels and for designing optimal thyroid hormone replacement therapy for patients with hypothyroidism.

A B S T R A C T The local conversion of thyroxine (T4), which is an important source of intracellular 3,5,3'-triiodothyronine (T3) in several rat tissues, has been subject of recent investigations. In the present study the regulation of this phenomenon in vivo was investigated in various peripheral tissues of the rat.Intact euthyroid and radiothyroidectomized (Tx) rats received a continuous intravenous infusion of [125I]T4 and ['31I]T3 until isotope equilibrium was attained. In addition to the labeled iodothyronines, Tx rats received a continuous intravenous infusion of 0.2 or 1.0 ,g carrier T4/100 g body wt per d, to create hypothyroid or slightly hypothyroid conditions, respectively. After the animals were bled and perfused the contribution of T3 derived from local conversion of T4 to T3 [Lc T3(T4)] to the total T3 in homogenates from several tissues and subcellular fractions from the liver, kidney, and anterior pituitary gland could be calculated. In all experiments T3 in muscle was derived exclusively from the plasma. In the cerebral cortex and cerebellum, however, most of the intracellular T3 was derived from the intracellular conversion of T4 to T3. It is demonstrated that for hypothyroid rats an increased relative contribution of Lc T3(T4) reduced the loss of total T3 in the brain. This phenomenon was also encountered for the anterior pituitary gland, although in this tissue the proportion of the total tissue T3, contributed by locally produced T3 was considerably lower than the values found for the cerebral cortex and cerebellum in all experiments.The present findings, regarding the source and quantity of pituitary nuclear T3 strongly suggest that both plasma T3 and T4 (through its local conversion into T3) play a role in the regulation of thyrotropin secretion. The contribution of Lc T3(T4) to the total pituitary nuclear T3 was of minor importance in euReceived for publication 23 August 1982 and in revised form 11 July 1983. thyroid rats (-20%), compared with that found for both groups in T4-supplemented athyreotic rats (-40%).The total T3 concentration in the liver decreased from euthyroid to hypothyroid rats and was associated with a decrease in the tissue/plasma T3 concentration gradient. A minor proportion of hepatic T3 was contributed by Lc T3(T4), which in fact decreased significantly from the euthyroid to the hypothyroid state. In contrast to other subcellular fractions from the liver, no Lc T3(T4) could be demonstrated in the nuclear fraction. It is suggested that the liver plays an important role with respect to regulation of the circulating T3 concentration.In the kidney, a very small proportion of the total T3 was derived from locally produced T3 in all experiments (4-7%). As found in the liver, all nuclear T3 appeared to be derived from the plasma. In contrast to the liver, subcellular T3 pools in the kidney seemed to be exchangeable.

Uptake of iodide is a prerequisite for radioiodine therapy in thyroid cancer. However, loss of iodide uptake is frequently observed in metastasized thyroid cancer, which may be explained by diminished expression of the human sodium iodide symporter (hNIS). Strategies to restore iodide uptake in thyroid cancer include the exploration of hNIS gene transfer into hNIS defective thyroid cancer. In this study, we report the stable transfection of a hNIS expression vector into the hNIS defective follicular thyroid carcinoma cell line FTC133. Stablely transfected colonies exhibited high uptake of Na125I, which could be blocked completely with sodiumperchlorate. hNIS mRNA expression corresponded with iodide uptake in semiquantitative polymerase chain reaction. Iodide uptake was maximal after 60 minutes, whereas iodide efflux was complete after 120 minutes. hNIS transfected FTC133 and control cell lines injected subcutaneously in nude mice formed tumors after 6 weeks. Iodide uptake in the hNIS transfected tumor was much higher than in the nontransfected tumor, which corresponded with hNIS mRNA expression in tumors.