Dear Professor,

This part is not about chicken broilers... BUT in humans, this researcher found low  levels of T3 with either normal levels of T4 or TSH. I thought this may help.

http://chriskresser.com/low-t3-syndrome-i-its-not-about-the-thyroid/

And in humans high T4 may means hyperthyroidism.In general, no matter what the TSH is doing, the T3 and T4 are doing the same as each other. See the chart as you scroll down.

https://labtestsonline.org/understanding/analytes/t4/tab/test/

In humans there can be is difficulty converting T4 to T3, This would mean there would be more T4 than T3. And may make too much rev.T3 instead.

https://www.holtorfmed.com/treating-thyroid-conversion-disorders-with-t3/

Again NOT chickens...but....thought it may help...

Now, in the chickens, is it possible that the lowering of the T4 from its original level is not significant? 

A 1985 article:  Gen Comp Endocrinol. 1985 Jul;59(1):91-9.

Effects of dietary thyroid hormones on growth, plasma T3 and T4, and growth hormone in normal and hypothyroid chickens. by

Leung FC, Taylor JE, Van Iderstine A. may be of interest. Here is the  link to the abstract. The actual article is about $30 US. 

http://www.ncbi.nlm.nih.gov/pubmed/4018556

In the following 1988 article, broiler chickens T4 were significantly higher  in a group of chickens handled with heat. 

In the book: Current Trends in Comparative Endocrinology

edited by B. Lofts, W. N. Holmes, the T3 and T4 are inversely related at light or dark feeding cycles.  T4 is increasing in chickens exposed to continuous dark AND not due to circadian rhythm AND                  pinealectomy did not change results ! Also fasting chickens T3 went down [T4 relatively goes up]  See page 517 and 518

https://books.google.com/books?id=46Lni02CsvYC&pg=PA517&lpg=PA517&dq=elevated+T4+in+chickens&source=bl&ots=JmBVFr45CB&sig=kqHgr-GuvOH4QrBO63KboImVSZw&hl=en&sa=X&ved=0CD4Q6AEwBGoVChMImNOBk4KVyQIVTOZjCh1mTw20#v=onepage&q=elevated%20T4%20in%20chickens&f=false

I do not know if this helps...But perhaps elevated T4 [inversely to T3] may be explained by handling, temperature and feeding time differences in groups or by different researchers.

I also found this: Zentralbl Veterinarmed A. 1996 Nov;43(9):521-30.

Responses of heat stressed chickens to exogenous reverse triiodothyronine (rT3).by Bobek S, Sechman A, Wieczorek E, Wrońska-Fortuna D, Koziec K, Niezgoda J. in which the tryglcerides were decreased not increased ..http://www.ncbi.nlm.nih.gov/pubmed/8968161

Poultry Production in Hot Climates edited by Nuhad Joseph Dagh See Pages 57,58 and 59.Refers to increase in triglycerides and in the 3rd paragraph on page 59 of this  section there is lowered T3. reasons are discussed.

https://books.google.com/books?id=ae4tJGRO-nYC&pg=PA59&lpg=PA59&dq=increase+in+triglycerides+and+decrease+in+T3+in+chickens&source=bl&ots=DWDFz4KOI2&sig=SjPRKMeSR8LX4Wd3qBP185PtrRc&hl=en&sa=X&ved=0CCMQ6AEwAWoVChMI8vaqm4uVyQIVWFqICh2nJg49#v=onepage&q=increase%20in%20triglycerides%20and%20decrease%20in%20T3%20in%20chickens&f=false

If you are questioning the truthfulness/accuracy of the data where all of the procedures were followed the same and exactly, then perhaps a repeat study is needed.

I hope this helps. I could not find a situation where highTriglycerides, low T3 and high T4 co-exist in the same article in regards to the same cause or disease.

Again hope this helps,

Respectfully,

Jeanetta Mastron

http://www.ncbi.nlm.nih.gov/pubmed/4018556

https://books.google.com/books?id=46Lni02CsvYC&pg=PA517&lpg=PA517&dq=elevated+T4+in+chickens&source=bl&ots=JmBVFr45CB&sig=kqHgr-GuvOH4QrBO63KboImVSZw&hl=en&sa=X&ved=0CD4Q6AEwBGoVChMImNOBk4KVyQIVTOZjCh1mTw20#v=onepage&q=elevated%20T4%20in%20chickens&f=false

https://books.google.com/books?id=ae4tJGRO-nYC&pg=PA59&lpg=PA59&dq=increase+in+triglycerides+and+decrease+in+T3+in+chickens&source=bl&ots=DWDFz4KOI2&sig=SjPRKMeSR8LX4Wd3qBP185PtrRc&hl=en&sa=X&ved=0CCMQ6AEwAWoVChMI8vaqm4uVyQIVWFqICh2nJg49#v=onepage&q=increase%20in%20triglycerides%20and%20decrease%20in%20T3%20in%20chickens&f=false

I´d look at your chickens feed, exactly if they have been fed with soy products.

Soy has shown (in humans) to affect tiroid function.