Ultrasound risk features guide whether a thyroid nodule should be biopsied. The finding that most often leads to fine-needle aspiration is the presence of suspicious characteristics, specifically irregular margins and microcalcifications, which meaningfully increase the likelihood of malignancy—most classically papillary thyroid carcinoma. These features push clinicians to obtain cytology to confirm or exclude cancer, even if the nodule isn’t very large. By contrast, a simple cyst with anechoic fluid is usually benign and monitored or aspirated for relief rather than biopsied for cancer; a homogeneous iso-echoic solid nodule with smooth margins tends to be low risk and may be managed with observation or biopsy only if larger or accompanied by other risk features; a comet-tail artifact is typically seen in benign colloid nodules and does not prompt biopsy.

Testosterone therapy is avoided when there are cancers that could be driven by androgens. The clearest absolute contraindication is known or suspected prostate cancer, because testosterone can stimulate prostate tissue and potentially accelerate tumor growth. That makes prostate cancer the primary contraindication to start or continue therapy. Controlled hypertension, mild hyperlipidemia, and age over 70 are not by themselves absolute blockers to testosterone treatment. Hypertension can be managed and monitored; mild lipid abnormalities can be addressed with lifestyle changes or therapy; and age alone doesn’t disqualify treatment, though all risks and benefits should be weighed in older patients.

Elevated IGF-1 indicates GH excess but doesn’t prove active acromegaly on its own. The next step is a dynamic test that shows whether GH secretion is truly autonomous: an oral glucose tolerance test with measurement of GH. In normal individuals, glucose intake suppresses GH to very low levels. In acromegaly, GH fails to suppress (typically remaining elevated, not dropping below about 1 ng/mL). This lack of suppression confirms biochemical acromegaly. After this confirmation, pituitary MRI with contrast is used to locate the adenoma. The other options don’t provide the confirmatory evidence needed: bone density assesses complications, prolactin elevation isn’t diagnostic of GH excess, and MRI is done after confirming the diagnosis.

C-peptide is released in equal amounts with endogenous insulin from functioning pancreatic beta cells, so it serves as a marker of the body's own insulin production. In established type 1 diabetes, autoimmune destruction severely reduces or eliminates beta-cell function, leading to very little or no endogenous insulin being produced. As a result, C-peptide levels fall to low (often undetectable) levels. Exogenous insulin therapy does not raise C-peptide because that insulin comes from outside the body. Some residual beta-cell activity can exist early on, but over time C-peptide typically becomes low, which is why low C-peptide is the typical finding in established type 1 diabetes.