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An Ex vivo Culture System to Study Thyroid Development
Published on: June 6, 2014
Endogenous thyroid hormones modulate pituitary somatotroph differentiation during chicken embryonic development
1Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland 20742, USA.
The Journal of Endocrinology
|January 8, 2004
Summary
Thyroid hormones are crucial for growth hormone cell differentiation in chicken embryos. This study shows that both natural and administered thyroid hormones, interacting with corticosterone, regulate somatotroph abundance during development.
Area of Science:
- Endocrinology
- Developmental Biology
- Cell Biology
Background:
- Growth hormone (somatotroph) cell differentiation in chicken embryos typically occurs between embryonic days 14-16.
- Previous research indicated corticosterone (CORT) induces somatotroph differentiation, and thyroid hormones augment this effect in vitro.
- The role of endogenous thyroid hormones in regulating somatotroph abundance during embryonic development was previously unclear.
Purpose of the Study:
- To investigate the hypothesis that endogenous thyroid hormones regulate somatotroph abundance during chicken embryonic development.
- To determine the impact of exogenous thyroid hormone administration on somatotroph differentiation in vivo.
- To elucidate the interaction between thyroid hormones and corticosterone in somatotroph development.
Main Methods:
- Plasma samples were collected from embryonic day (e) 9 to e 14 to measure CORT and thyroid hormone levels.
- Fertile eggs received thyroxine (T4) and triiodothyronine (T3) or methimazole (thyroid hormone synthesis inhibitor) at specific embryonic days.
- Somatotroph differentiation was assessed in developing chick embryos, with some groups receiving T3 replacement therapy.
Main Results:
- Plasma CORT and thyroid hormone levels increased progressively leading up to normal somatotroph differentiation (e 13-14).
- Exogenous T4 and T3 administration on e 11 resulted in premature somatotroph differentiation on e 13.
- Methimazole treatment on e 9 inhibited somatotroph differentiation, an effect reversed by T3 replacement on e 11.
Conclusions:
- Endogenous thyroid hormone synthesis likely contributes to normal somatotroph differentiation in chicken embryos.
- Exogenous thyroid hormone administration can modulate somatotroph abundance during embryonic development.
- The in vivo effects of thyroid hormones on somatotroph differentiation appear to involve interactions with endogenous glucocorticoids.
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