Thyroid hormone dynamics during the nursing period in harbour seals, Phoca vitulina
The postnatal period in phocid seals is metabolically demanding, requiring mobilization of maternal energy stores, which are then transferred via the milk for subsequent deposition in the pup. Thyroid hormones may be important modulators of these processes, and so we monitored circulating levels of...
| Published in: | Canadian Journal of Zoology |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1998
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/z97-156 http://www.nrcresearchpress.com/doi/pdf/10.1139/z97-156 |
| Summary: | The postnatal period in phocid seals is metabolically demanding, requiring mobilization of maternal energy stores, which are then transferred via the milk for subsequent deposition in the pup. Thyroid hormones may be important modulators of these processes, and so we monitored circulating levels of free and total thyroxine (T 4 ), triiodothyronine (T 3 ), and reverse T 3 (rT 3 ) in 13 free-ranging female harbour seals (Phoca vitulina) and their pups for up to 25 days post partum. Early total and free T 4 levels, percentage of free T 4 , total and free T 3 levels, rT 3 levels, and rT 3 :T 3 ratios were significantly higher in pups than in mothers. Total and free T 4 levels, percentage of free T 4 , free T 3 and rT 3 , levels, and rT 3 :T 3 ratios in pups decreased significantly over the lactation period, while maternal total and free T 4 levels increased significantly. Our findings highlight the dynamic nature of thyroid hormones and their involvement in regulating metabolism throughout this important period. This is the first report examining free T 3 and rT 3 levels in phocid seals. |
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