Gh effect on T3 levels

: J Clin Endocrinol Metab. 1988 Nov;67(5):1111-4. Related Articles, Links


The acute effects of human growth hormone administration on thyroid function in normal men.

Grunfeld C, Sherman BM, Cavalieri RR.

Department of Medicine, University of California, San Francisco.

GH replacement therapy may lead to alterations in serum TSH and/or thyroid hormone values in GH-deficient patients, but there is no consensus on the explanation for these changes. We examined the effect of GH administration (0.125 mg, sc, daily for 4 days) on thyroid function in 20 normal men. Serum T4 levels decreased by 8%, and serum free T4 index values decreased by 5%. In contrast, serum T3 levels increased by 21%; serum rT3 did not change. These changes were accompanied by a 54% decrease in the mean serum TSH level. While it is not possible to draw conclusions about hormone production and disposal rates from changes in serum levels, these data are most consistent with enhanced extrathyroidal (including intrapituitary) conversion of T4 to T3 and a compensatory decrease in TSH secretion.

PMID: 3182961 [PubMed - indexed for MEDLINE]

Intesting read. Wonder how much GH they used. That tired lethargic feeling you get on GH is due to decreased T3. That's why I was wondering about the GH dose.

The article says they used 0.125 mg's daily which resulted in a 21% increase in T3 serum levels. There is definitely a permissive effect between GH and thyroid activity (specifically T3). I have witnessed this personally. It would not surprise me if the pituitary gland bypassed the hypothalamus to increase T3 levels in an attempt to maintain parity between thyroid activity and GH levels (increased by exo GH). The article mentions the possibility of converting T3 from T4. TSH is likely inhibited via a hypothalamus-pituitary negative feedback loop.

The sleepiness probably comes from increased levels of melatonin.

Nice info Golden.