Sex Hormone Binding Globulin (SHBG) is a protein produced by the liver that binds to sex hormones such as estrogen, testosterone, and thyroid hormone. Its role is regulatory: when hormones are bound to SHBG, they are not “free” or biologically active. Only the unbound (free) portion of a hormone is available to act on tissues in the body.
Why SHBG Can Increase When Starting Oestra®
When you begin Oestra®, SHBG levels often rise. This is a normal physiologic response, as estradiol - the form of estrogen used in Oestra® - stimulates SHBG production in the liver.
As SHBG increases, it can temporarily bind more thyroid hormone and, in some cases, testosterone. This can reduce the amount of free (active) hormone available to tissues, even if hormone levels were previously normal on lab work.
How This May Feel in the Body
For some women, a temporary rise in SHBG may show up as:
New-onset or worsening low mood, fatigue, or a general sense of “blahs”
Lower energy or stamina
Water retention or puffiness
A feeling of slower metabolism
These symptoms may feel surprising, especially if thyroid labs were normal prior to starting Oestra®. In many cases, the thyroid hormone is present but temporarily bound by SHBG rather than freely available.
What Typically Happens Over Time
In most cases, this effect evens out over several weeks as the body adapts and establishes a new hormonal balance. This adjustment phase is not harmful and is considered a normal physiologic response for some women when starting hormone therapy.
Supportive Steps We May Recommend
If fatigue, low mood, or water retention lingers, your care team may suggest supportive measures such as:
Thyroid support, including iodine (if you are not already taking it) and selenium, or a thyroid-support supplement
A lower-carbohydrate diet, which may help bring SHBG levels down
Nettle root, in some cases, to help reduce SHBG and increase free hormone availability
If fatigue is the primary symptom and iodine is not already part of your routine, SHBG-related thyroid binding is often considered first.
The Role of Protein During Hormone Adjustment
Adequate protein intake is especially important when adjusting to Oestra®, as protein plays several key roles in hormone balance:
Slows the metabolism of estrogen in the liver
Supports the synthesis of SHBG in a balanced and regulated way
Provides essential amino acids for cellular repair, including the skin, muscles, brain, and uterus
Consistent protein intake can help support metabolic stability and overall adaptation during this phase.
When to Look More Closely at Thyroid Function
If fatigue or low mood is accompanied by symptoms such as constipation or persistent water retention, additional thyroid evaluation may be appropriate. In these cases, thyroid function may be genuinely low rather than simply bound by SHBG, and your provider may recommend thyroid lab testing.
In Summary
Oestra® can raise SHBG, which may temporarily reduce the availability of free thyroid hormone. For some women, this can present as fatigue, low mood, or feeling “off” during the early adjustment phase. This response is not harmful and is usually temporary. With time, adequate protein intake, appropriate thyroid support, and individualized clinical guidance, most women find that their energy and sense of balance improve again.
If symptoms persist or feel concerning, we encourage you to reach out to your care team so we can support you through this transition.