Should You Recheck Your FSH After Hyperthyroidism Resolution?
Yes, you should absolutely recheck your FSH level now that your hyperthyroidism has been treated and your symptoms have resolved. Your initial FSH of 10.5 IU/L was likely elevated due to the severe iatrogenic hyperthyroidism, and the resolution of your erectile dysfunction, libido issues, and semen changes strongly suggests the hormonal disturbance was temporary.
Why Hyperthyroidism Elevated Your FSH
Hyperthyroidism directly increases gonadotropin levels in men. Research demonstrates that hyperthyroid men have significantly elevated basal LH and FSH levels compared to normal men, with these elevations approaching normal during or after treatment of hyperthyroidism 1.
Thyroxine (T4) specifically drives FSH elevation. Studies show that when normal men are given T4 to induce hyperthyroidism, their gonadotropin levels increase similarly to spontaneously hyperthyroid patients, whereas T3 administration does not produce the same effect 1.
The mechanism involves altered hypothalamic-pituitary-gonadal axis function. Hyperthyroid men exhibit hyperresponsiveness of LH to GnRH administration, indicating disrupted feedback mechanisms at the pituitary level 2.
Evidence That Your FSH Should Normalize
Primary hypothyroidism causes the opposite effect (hypogonadotropic hypogonadism), which is reversible with thyroid hormone replacement. This demonstrates that thyroid dysfunction's effects on the reproductive axis are bidirectional and reversible 2.
Your clinical improvement is highly predictive of hormonal normalization. The fact that your ED, low libido, and semen changes have all resolved indicates that your hypothalamic-pituitary-gonadal axis has likely recovered from the hyperthyroid state 2.
Weight loss and severe metabolic stress from hyperthyroidism can independently affect reproductive hormones. Your weight loss during the hyperthyroid episode would have contributed to hormonal disruption, and weight restoration typically normalizes these parameters 3.
Recommended Testing Protocol
Recheck FSH, LH, and total testosterone now that you are euthyroid. Wait at least 6-8 weeks after achieving stable thyroid function to allow the hypothalamic-pituitary-gonadal axis to fully recover 4.
Ensure TSH and free T4 are in the normal reference range when you recheck reproductive hormones. Thyroid function tests should be stable and normal, as even subclinical thyroid dysfunction can affect gonadotropin levels 5.
If FSH remains elevated (>10 IU/L) after confirmed euthyroid status for 2-3 months, then consider further evaluation. At that point, a semen analysis and consultation with a reproductive endocrinologist or urologist would be appropriate to assess for primary testicular dysfunction 6.
Why Your Initial FSH of 10.5 IU/L Is Not Concerning in Context
FSH of 10.5 IU/L is only mildly elevated and falls within the range commonly seen in hyperthyroid men. This level does not suggest severe testicular damage, especially given your symptom resolution 1.
The temporal relationship between severe hyperthyroidism and FSH elevation strongly suggests causation. Your symptoms (ED, low libido, semen changes) and FSH elevation all occurred during the hyperthyroid state and resolved together, indicating a reversible process 2.
Iatrogenic hyperthyroidism from excessive thyroid hormone is particularly likely to cause transient gonadotropin elevation. The severity of your hyperthyroidism (with weight loss) indicates significant thyroid hormone excess, which would be expected to substantially elevate FSH 1, 3.
Critical Pitfalls to Avoid
Do not assume permanent fertility impairment based on a single FSH measurement during active thyroid disease. Thyroid function tests can be misleading when performed during metabolic instability, and the same principle applies to reproductive hormones 5.
Do not pursue invasive fertility testing or treatment until thyroid function has been stable and normal for at least 2-3 months. Premature evaluation will yield unreliable results and may lead to unnecessary interventions 4.
Avoid rechecking FSH too soon after thyroid normalization. The hypothalamic-pituitary-gonadal axis requires time to re-equilibrate after resolution of hyperthyroidism, typically 6-8 weeks minimum 4.
Long-Term Fertility Considerations
Even if radioactive iodine had been used to treat your hyperthyroidism (which doesn't appear to be your case), testicular function typically recovers by 18 months post-therapy. Studies show that RAI causes transient FSH elevation and impaired spermatogenesis that usually resolves 2, 6.
The absorbed radiation dose to testes from standard RAI treatment for hyperthyroidism is minimal (approximately 39 microGy/MBq) and causes only marginal changes in germinal epithelium function. This is relevant only if you received RAI, but demonstrates that even direct gonadal radiation from thyroid treatment is typically reversible 6.
Your prognosis for normal fertility is excellent given complete symptom resolution. The return of normal erectile function, libido, and semen characteristics indicates intact testicular and hormonal function 2.