Hypothalamic Thyrotropin Releasing Factor Activity and Pituitary Responsiveness during Development in the Rat

Conklin, P. M.; Schindler, William J.; Hull, Stacy

doi:10.1159/000122133

Cited by 18 publications

(6 citation statements)

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“…In this study, fetal plasma TSH also increased signifi cantly as the result of maternal TRH injection, though the magnitude of the response differed from previously reported studies (19). Although thyroid axis function does not mature in the rat until 2-3 weeks postnatally (4,8,18,25), some thyroid-pituitary feedback interaction does occur (14,15). The greater magnitude of response of plasma TSH to TRH observed in the fetal young of deficient dams may indicate a heightened sensitivity to TRH, and suggest that circulating thyroid hormones may be depressed in these fetuses.…”

Section: Discussioncontrasting

confidence: 80%

Effects of Protein Deficiency and Food Restriction during Gestation in Rats on Maternal and Fetal Plasma and Pituitary Thyrotropin Levels

Hastings-Roberts¹,

Zeman²

1979

Ann Nutr Metab

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The effects of protein deficiency and food restriction during pregnancy on maternal and fetal plasma and pituitary thyrotropin (TSH) levels were investigated on day 20 of gestation. The same parameters were also determined following administration of exogenous thyrotropin-releasing hormone (TRH). Maternal plasma and pituitary basal TSH concentrations were significantly elevated in protein deficiency. TRH injection to protein-deficient dams caused a marked reduction in pituitary TSH concentration, suggesting that the elevated plasma TSH seen in uninjected dams might be due to decreased metabolic clearance rather than to hypersecretion by the pituitary. Food restriction resulted in significant lowering of plasma TSH, but did not alter pituitary TSH in comparison to that of control dams. TRH administration had no effect on pituitary TSH concentration in food-restricted and control dams. Pituitaries of fetal young of protein-deprived dams were significantly smaller and contained significantly less total TSH, accompanied by a slight reduction in circulating plasma TSH. These observations are suggestive of developmental and functional retardatation of the fetal pituitary. Fetal pituitary TSH was unaffected by TRH administration to control and food-restricted dams whereas, in young of protein-deprived females, total gland TSH was reduced.

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Section: Discussioncontrasting

confidence: 80%

Effects of Protein Deficiency and Food Restriction during Gestation in Rats on Maternal and Fetal Plasma and Pituitary Thyrotropin Levels

Hastings-Roberts¹,

Zeman²

1979

Ann Nutr Metab

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“…TRH has been shown to affect the synthesis and release of TSH in the rat during the fetal and neonatal period (5). Although there have been reports on the hypothalamic content of bioactive and immunoreactive TRH (6,7) during the postnatal development, no information is yet available on the evolution pattern of TRH in rat fetuses and on the evolution of TRH in the extrahypo thalamic regions of the brain during the neo natal period.…”

Section: Introductionmentioning

confidence: 99%

Developmental Changes in Brain TRH and in Plasma and Pituitary TSH and Prolactin Levels in the Rat

Oliver¹,

Eskay²,

Porter³

1980

Neonatology

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TRH in the hypothalamus and the rest of the brain, as well as TSH and prolactin in the pituitary gland and the plasma have been determined by radioimmunoassay in rats varying in age (10- to 22-day-old fetuses and 1- to 60-day-old rats). TRH is first detected on the 16th day of gestation and its maximum increase occurs during the first 3 weeks of life both in the hypothalamus and the rest of the brain. The evolution patterns of TSH and prolactin in the plasma and the pituitary gland are discussed in relation to TRH levels in the brain and in the hypothalamus.

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“…N UMEROUS studies (1)(2)(3)(4)(5)(6) have shown that maturation of the rat hypothalamic-pituitary axis occurs to a large extent through the neonatal period and that the newborn rat is relatively hypothyroid (7). To study this maturation more specifically, we have measured the hypothalamic content of thyrotropin-releasing hormone (TRH) and the pituitary content of thyroid-stimulating hormone (TSH) during the first 50 days of life in the rat, as well as the serum concentrations of TSH, thyroxine (T 4 ), and triiodothyronine (T 3 ).…”

mentioning

confidence: 99%

Development of the Hypothalamic-Pituitary-Thyroid Axis in the Neonatal Rat

1975

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The hypothalmic content of thyrotropin-releasing hormone (TRH), the pituitary concentration of thyroid-stimulating hormone (TSH), and the serum concentrations of TSH, thyroxine (T4), and triiodothyronine (T3) have been determined at different intervals during the first 50 days following birth in the rat. From a minimum concentration of 1 pg/mug protein at birth, the hypothalamic concentration of TRH increased to a maximum of 5 to 6 pg between 16 and 28 days of age. Serum and pituitary TSH concentrations increased to maximum levels by the end of the first post-natal week; the elevated hormone levels were then maintained to the end of the third post-natal week. Circulating thyroid hormone concentrations were very low at birth. T4 increased rapidly between days 4 and 16 to reach a peak concentration of 6 mug/100 ml, while T3 followed a parallel pattern with a peak concentration of 108 ng/100 ml obtained only at day 28. These data indicate that, in the rat, components of the hypothalamic-pituitary-thyroid axis develop simultaneously during the post-natal period.

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Hypothalamic Thyrotropin Releasing Factor Activity and Pituitary Responsiveness during Development in the Rat

Cited by 18 publications

References 0 publications

Effects of Protein Deficiency and Food Restriction during Gestation in Rats on Maternal and Fetal Plasma and Pituitary Thyrotropin Levels

Effects of Protein Deficiency and Food Restriction during Gestation in Rats on Maternal and Fetal Plasma and Pituitary Thyrotropin Levels

Developmental Changes in Brain TRH and in Plasma and Pituitary TSH and Prolactin Levels in the Rat

Development of the Hypothalamic-Pituitary-Thyroid Axis in the Neonatal Rat

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