Reproduction and thyroid function in red deer (Cervus elaphus) hinds
Reproduction and thyroid function in red deer (Cervus elaphus) hinds
Crawford, Janet L.
Crawford, Janet L.
Date
1993
Type
Dissertation
Fields of Research
ANZSRC::070206 Animal Reproduction
Abstract
This experiment was conducted to investigate the effect oestrogens have upon thyroid
and pituitary responsiveness to stimulation by thyrothropin-releasing hormone (TRH) in
the red deer (Cervus elaphus) hind.
The first group of hinds, consisting of three ovariectomized and three entire hinds, were
subjected to a TRH challenge (5 µl TRH in 2 ml saline solution) at 0800 h on 17 March
1993. Blood samples were collected at -60, -30, -15, 0, 5, 10, 15, 30, 45, 60, 90 and 120
minutes after the TRH injection. This procedure was repeated on a second group of
hinds, consisting of three ovariectomized and three entire hinds, at 0810 h the following
day.
The entire group of hinds (n=6) exhibited a significantly higher mean plasma T₃
response to the TRH challenge compared with that of the ovariectomized group of hinds
(peak values = 2.86 ± 0.55 ng.ml⁻¹ and 2.61 ± 0.55 ng.ml⁻¹ respectively). The
ovariectomized hinds had a non-significantly higher mean basal T₃ concentration
compared with that of the entire hinds before the TRH challenge (2.32 ± 0.63 ng.ml⁻¹
and 2.18 ± 0.40 ng.ml⁻¹ respectively).
The entire hinds also exhibited a significantly higher mean plasma prolactin response
compared with that of the ovariectomized hinds (42.70 ± 65.62 ng.ml⁻¹ and 7.33 ± 17.82
ng.ml⁻¹ respectively), however there was no significant difference between the mean
plasma basal prolactin concentrations between the two groups before the TRH
challenge.
There was no significant response of mean plasma LH concentrations in either the
ovariectomized or entire group of hinds after the TRH challenge. However there was a
small non-significant rise in mean plasma LH concentrations immediately following the
TRH injection in both the ovariectomized and entire group of hinds.
In conclusion, results from this study demonstrate that oestrogens enhance the thyroid
glands and pituitary gland respo~siveness to TRH with respect to T₃ and prolactin
release respectively in the red deer hind.
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