Sex Differences in Brain Thyroid Hormone Levels during Early Post-Hatching Development in Zebra Finch (Taeniopygia guttata)

PLoS One. 2017 Jan 6;12(1):e0169643. doi: 10.1371/journal.pone.0169643. eCollection 2017.


Thyroid hormones are closely linked to the hatching process in precocial birds. Previously, we showed that thyroid hormones in brain had a strong impact on filial imprinting, an early learning behavior in newly hatched chicks; brain 3,5,3'-triiodothyronine (T3) peaks around hatching and imprinting training induces additional T3 release, thus, extending the sensitive period for imprinting and enabling subsequent other learning. On the other hand, blood thyroid hormone levels have been reported to increase gradually after hatching in altricial species, but it remains unknown how the brain thyroid hormone levels change during post-hatching development of altricial birds. Here, we determined the changes in serum and brain thyroid hormone levels of a passerine songbird species, the zebra finch using radioimmunoassay. In the serum, we found a gradual increase in thyroid hormone levels during post-hatching development, as well as differences between male and female finches. In the brain, there was clear surge in the hormone levels during development in males and females coinciding with the time of fledging, but the onset of the surge of thyroxine (T4) in males preceded that of females, whereas the onset of the surge of T3 in males succeeded that of females. These findings provide a basis for understanding the functions of thyroid hormones during early development and learning in altricial birds.

MeSH terms

  • Animals
  • Brain / growth & development*
  • Brain / metabolism*
  • Female
  • Finches / physiology*
  • Gene Expression
  • Iodide Peroxidase / genetics
  • Iodide Peroxidase / metabolism
  • Male
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Thyroid Hormone / metabolism
  • Sex Characteristics*
  • Thyroid Hormones / blood
  • Thyroid Hormones / metabolism*


  • RNA, Messenger
  • Receptors, Thyroid Hormone
  • Thyroid Hormones
  • Iodide Peroxidase

Grants and funding

This work was supported by the Grant-in-Aid for Scientific Research on Innovative Areas "Memory dynamism" (26115522) from the Ministry of Education, Culture, Sports, Science and Technology (K.J.H.),; The Grant-in-Aid for Scientific Research on Innovative Areas "Adaptive Circuit Shift" (15H01449) from the Ministry of Education, Culture, Sports, Science and Technology (K.J.H),; and Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science ( (N.A., 24790089; S.Y., 24590096, 15K07945; T.M., 25291071; K.W., 25290063; K.J.H., 26440182). Additional support was received from: 1. The Naito Foundation (K.J.H.); 2. The Japan Foundation of Applied Enzymology (K.J.H.); 3. NOVARTIS Foundation (Japan) for the Promotion of Science, 13-113 (K.J.H.); 4. The Uehara Memorial Foundation (K.J.H., S.Y.); 5. The Sagawa Foundation for Promotion of Cancer Research (S.Y.); 6. Grant for Basic Science Research Projects from the Sumitomo Foundation, 130063 (S.Y.); 7. Takeda Science Foundation (S.Y.); and 8. The Research Foundation for Pharmaceutical Sciences (S.Y.).