Is supplementing T-3/T-4 necessary while using HGH!? The broad answer is no with a few exceptions. But first it's important to know why Thyroxine levels may decline during early GH therapy.
Quite simply because GH cause the production and secretion of Insulin Growth Factor to increase the quantity of T-3:4 required to meet the metabolic demand also increased.
Moreover the the amount of T-3/4 consumed if directly
proportional to the GH dosage.
Consequently the first few weeks or moths of GH therapy may result in a relative a decrease in thyroxine levels.
However all is not lost, because almost all human hormonal systems, including the thyroid gland, operate on a relatively tight feedback control mechanism to maintain optimal T levels.
Thus with the passage of time, the lowered thyroxine level causes the increased secretion of pituitary TSH, which in turn results in the increased production of thyroxine by the thyroid gland..
Therefore unless you have an "under active" thyroid prior to initiating thyroid therapy T-3/4 supplementation circumvents the natural physiologic response to low Thyroxine, and is unwarranted IMO.
Consequently it's relatively important to obtain TFTs prior to GH use, with
the objective being the detection of asymptomatc hypothyroid patients.
Because the use of GH in these folks will often unveil sub-clinical hypothyroidism. .
It's also very important to know MANY of the studies which either recommended Thyroid therapy or suggested close observation and/or testing for thyroid dysfunction may be warranted, were performed on children with short stature children, congenital syndromes, genetic disorders or elderly adults, etc.
These patient subgroups are well known to have limited thyroid reserve and are by their very nature hypothyroid prone.
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