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Changes in thyroid function and gonadotrophin activity during sexual development in ducks Anas sp. (Aves: Anatidae)
Author(s) -
Klandorf H.,
Harvey S.
Publication year - 1984
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1984.tb06047.x
Subject(s) - biology , endocrinology , medicine , sexual maturity , hatching , thyroid , thyroid function , luteinizing hormone , hormone , anatidae , testosterone (patch) , sexual dimorphism , zoology
Age‐related changes in plasma iodohormone concentrations in male and female Aylesbury and Khaki Campbell ducklings were determined between the second week after hatching and sexual maturity. In both sexes and strains the concentration of total thyroxine (T 4 ) and the free thyroxine index (FT 4 1) were low during the first 6–8 weeks after hatching. A marked increase in the T 4 and FT 4 1 occurred when the ducklings were nine weeks old; T 4 progressively increased over the following four weeks and remained high thereafter. The T 4 concentration in both sexes was directly related to age. Concentrations of total tri‐iodothyronine (T 3 ) were more variable than T 4 but were highest before sexual maturation and inversely age‐related. An age‐related decline in free tri‐iodothyronine index (FT 3 1) was observed during the first nine weeks. The possibility that these maturational changes in thyroid function may reflect changes in gonadal activity was assessed by measuring the concentration of luteinizing hormone (LH) in the same plasma samples. Although plasma LH increased with age, in all cases the increase occurred after changes in the thyroid hormones were observed. Moreover, the maturational pattern of LH was related to sex and strain whereas thyroid function was unaffected by sex or strain. These results demonstrate reciprocal changes in plasma T 3 and T 4 levels in ducks during sexual development, although the stimuli responsible and physiological significance are uncertain.